Einstein was born on 14 March 1879 in Ulm, in the Kingdom of Württemberg within the German Empire, to Hermann Einstein, an engineer and salesman, and Pauline Koch. His parents were secular Ashkenazi Jews, and his younger sister, Maria (known as Maja), was born two years later.¹³ In 1880, the family relocated to Munich, where Hermann and his brother Jakob established Elektrotechnische Fabrik J. Einstein & Cie, an electrical equipment manufacturing firm specializing in direct current systems. Although Einstein was slow to speak in early childhood, he excelled academically from an early age. He attended a Catholic elementary school in Munich before enrolling at the Luitpold Gymnasium, where he clashed with the school's strict, rote-learning pedagogy.¹⁴¹⁵ During his youth, he independently studied Euclidean geometry, differential and integral calculus, and Immanuel Kant's philosophy.

In 1894, after failing to secure municipal contracts, the family business collapsed, and Einstein's parents moved to Milan and then Pavia in Italy. Left behind in Munich to complete his secondary schooling, the fifteen-year-old Einstein grew resentful of Prussian educational discipline and the prospect of compulsory military service. At the end of 1894, he withdrew from the gymnasium and joined his family in Pavia, where he composed an early scientific essay examining the state of the ether in magnetic fields.

After failing the general subjects portion of the entrance examination for the Swiss Federal Polytechnic School in Zurich in 1895—despite earning exceptional marks in physics and mathematics—Einstein completed his secondary schooling at the Argovian cantonal school in Aarau, Switzerland.¹⁶ In early 1896, with his father's approval, he formally renounced his citizenship in the Kingdom of Württemberg to avoid German military conscription, remaining stateless until he acquired Swiss citizenship in February 1901. In October 1896, at age seventeen, he enrolled in the four-year mathematics and physics teaching diploma program at the Zurich Polytechnic. There he met Mileva Marić, a Serbian student and the sole woman in his academic section.¹⁷ Einstein graduated in 1900, and after two years of temporary tutoring and teaching posts, he was appointed a technical expert third class at the Federal Office for Intellectual Property—the Swiss Patent Office—in Bern in June 1902, a position secured with the help of his friend Marcel Grossmann's father.

Evaluating patent applications for electromagnetic devices in Bern left Einstein ample time to pursue theoretical physics independently. In 1905, at the age of twenty-six, he completed his doctoral dissertation for the University of Zurich on determining molecular dimensions and submitted four landmark papers to the German journal Annalen der Physik. Historians of science refer to 1905 as Einstein's annus mirabilis (miracle year).

The first paper, received in March 1905 and titled "On a Heuristic Viewpoint Concerning the Production and Transformation of Light," built upon Max Planck's black-body radiation work to propose that light consists of discrete, localized packets of energy—which Einstein called light quanta, later termed photons—with energy proportional to frequency ($E = hf$).¹⁸¹⁹ He used this hypothesis to explain the photoelectric effect, showing why light shining on a metal surface ejects electrons only above a threshold frequency, regardless of the light's intensity. The second paper, published in July, provided a stochastic mathematical model for Brownian motion, demonstrating that the erratic movement of microscopic particles suspended in a stationary liquid results from collisions with surrounding fluid molecules. When French physicist Jean Perrin experimentally verified these predictions in 1908, it settled longstanding scientific debates by proving the physical reality of atoms and molecules.

The third paper, "On the Electrodynamics of Moving Bodies," introduced the special theory of relativity. Reconciling James Clerk Maxwell's electromagnetism with the mechanics of moving bodies, Einstein discarded the concept of a luminiferous ether and rested his theory on two postulates: that the laws of physics are identical in all inertial frames of reference, and that the speed of light in a vacuum is constant for all observers regardless of the motion of the light source. From these principles, he deduced time dilation, length contraction, and the relativity of simultaneity, abolishing Isaac Newton's concepts of absolute space and time. His fourth paper, a brief follow-up titled "Does the Inertia of a Body Depend Upon Its Energy Content?", demonstrated that mass and energy are interchangeable manifestations of the same physical entity, later expressed as $E = mc^2$, where $c$ is the speed of light.

Senior physicists, notably Max Planck, recognized the importance of the 1905 publications, and Max von Laue traveled to Bern to meet the young patent examiner. In 1908, Einstein was appointed a Privatdozent (unsalaried lecturer) at the University of Bern. The following year, he resigned from the patent office to become an associate professor of theoretical physics at the University of Zurich. He accepted a full professorship at the Charles-Ferdinand University in Prague in 1911 before returning to his alma mater in Zurich as a professor in 1912. In 1914, he relocated to Berlin after being elected to the Prussian Academy of Sciences, appointed a professor at the Humboldt University of Berlin without teaching obligations, and named director of the Kaiser Wilhelm Institute for Physics, regaining German citizenship in the process.

Throughout the 1910s and 1920s, Einstein continued to make foundational contributions to quantum physics. In 1916 and 1917, he introduced the concepts of spontaneous and stimulated emission of radiation, laying the theoretical groundwork for the laser. In 1924, Indian physicist Satyendra Nath Bose sent Einstein a paper deriving the Planck black-body spectrum by treating light quanta as indistinguishable particles. Einstein translated Bose's work into German, arranged for its publication, and extended the statistical method to matter particles, predicting that cooling a gas of bosons to near absolute zero would cause the atoms to coalesce into a single macroscopic quantum state, now known as a Bose–Einstein condensate.

Despite his role in founding quantum theory, Einstein grew increasingly dissatisfied with the probabilistic direction the field took in the mid-1920s under Niels Bohr, Werner Heisenberg, and Max Born.²²²³ According to the Copenhagen interpretation championed by Bohr, quantum systems exist in a superposition of states described by a wave function, and physical properties acquire definite values only upon measurement.²⁴ Einstein rejected this indeterminism, famously remarking in correspondence that God does not play dice with the universe. He maintained a realist philosophical position: that physical systems possess objective, definite properties independent of observation, and that any theory relying solely on probabilities must be an incomplete description of an ensemble of systems rather than a complete account of individual events.²⁵

At the fifth and sixth Solvay Conferences in 1927 and 1930, Einstein engaged in a celebrated series of public debates with Bohr, devising intricate thought experiments to challenge Heisenberg's uncertainty principle, which Bohr parried by invoking complementarity and even Einstein's own relativistic principles.²⁶ In 1935, working at Princeton with younger colleagues Boris Podolsky and Nathan Rosen, Einstein published a paper titled "Can Quantum-Mechanical Description of Physical Reality Be Considered Complete?", introducing what became known as the EPR paradox. Examining pairs of particles that have interacted and separated—a phenomenon Erwin Schrödinger termed entanglement—they argued that if measuring one particle instantaneously determines the state of its distant partner, then either quantum mechanics violates locality through "spooky action at a distance" or the wave function is incomplete because the particles already possessed hidden, predetermined properties. Although subsequent experimental tests of Bell's theorem decades after Einstein's death refuted local realism in favor of quantum mechanics, the EPR paper established quantum entanglement as a central subject of modern physics and quantum information science.

For the final three decades of his life, Einstein grew scientifically isolated from the mainstream physics community, which focused on applying quantum mechanics to nuclear and particle physics. Rejecting the emerging consensus, he devoted his research to constructing a unified field theory—a geometric framework intended to unite gravitation and electromagnetism under a single set of deterministic equations, from which quantum particles and probabilities would emerge as secondary consequences. He pursued this goal without success until his death.

While studying in Zurich, Einstein fell in love with his classmate Mileva Marić. In early 1902, prior to their marriage, Marić gave birth to a daughter named Lieserl at her parents' home in Novi Sad; the child's ultimate fate is unknown to historians, with surviving correspondence suggesting she either died of scarlet fever in infancy in 1903 or was given up for adoption.²⁷ Einstein and Marić married in Bern on 6 January 1903. They had two sons born in Switzerland: Hans Albert (born 1904), who later became a professor of hydraulic engineering at the University of California, Berkeley, and Eduard (born 1910), who developed schizophrenia at age twenty and spent most of his adult life in the Burghölzli psychiatric clinic in Zurich.²⁸ While some writers have speculated that Marić co-authored Einstein's 1905 papers, historians of physics who have examined their correspondence conclude that she served as an intellectual sounding board and supportive partner rather than a co-creator of his scientific results.

In 1912, Einstein began an affair with his cousin Elsa Löwenthal (née Einstein), who was related to him on both his maternal and paternal sides.²⁹ After Einstein and Marić moved to Berlin in 1914, their marriage deteriorated rapidly, and Marić returned to Zurich with their two sons a few months later. During World War I, when Einstein suffered from severe stomach ailments, Elsa nursed him back to health. As part of a divorce settlement finalized in February 1919, Einstein agreed to transfer to Marić the monetary proceeds of the Nobel Prize he anticipated winning, a promise he fulfilled in 1923. Einstein married Elsa on 2 June 1919 and helped raise her two daughters from her previous marriage, Ilse and Margot. Elsa managed his household and public correspondence until her death from heart and kidney ailments in Princeton in December 1936.

Einstein's public prominence made him a target of right-wing nationalists and antisemites in Weimar Germany, including proponents of the Deutsche Physik movement who denounced relativity as "Jewish physics." In January 1933, while Einstein was on a visiting professorship at the California Institute of Technology, Adolf Hitler was appointed Chancellor of Germany. After Nazi authorities raided Einstein's Berlin apartment and confiscated his summer house in Caputh, he traveled to Belgium in March 1933, surrendered his German passport at the German consulate in Antwerp, and resigned from the Prussian Academy of Sciences. In October 1933, he permanently relocated to the United States to take up a position at the newly established Institute for Advanced Study in Princeton, New Jersey, moving into a house at 112 Mercer Street in 1935. Retaining his Swiss citizenship, he became a naturalized citizen of the United States in 1940.

A lifelong opponent of militarism, Einstein had been one of only four German academics in October 1914 to sign the anti-war "Manifesto to the Europeans," a rebuttal to the nationalistic "Manifesto of the Ninety-Three" that defended Germany's conduct in World War I.³⁰ In the 1920s, he championed conscientious objection and international disarmament, admiring Mahatma Gandhi's philosophy of nonviolent resistance.³¹ However, the rise of Nazi Germany caused him to revise his absolute pacifism, arguing that military force was necessary to defeat fascism.

In July 1939, physicists Leo Szilard and Eugene Wigner visited Einstein to warn that Nazi Germany might attempt to construct an atomic bomb using newly discovered nuclear fission. In August 1939, Einstein signed a letter drafted by Szilard to President Franklin D. Roosevelt, urging the United States government to accelerate uranium research. This warning contributed to the eventual establishment of the Manhattan Project, though Einstein himself was denied a security clearance by US intelligence agencies due to his pacifist and left-wing affiliations and played no role in designing nuclear weapons. Appalled by the atomic bombings of Hiroshima and Nagasaki in 1945, he later called signing the letter to Roosevelt the one great mistake of his life. After the war, he chaired the Emergency Committee of Atomic Scientists and campaigned for supranational control of nuclear weapons under a strengthened world government. One week before his death in April 1955, he signed the Russell–Einstein Manifesto with British philosopher Bertrand Russell, warning of the existential peril of thermonuclear warfare.³²

In domestic and international politics, Einstein advocated for civil rights, democratic socialism, and Labor Zionism. In Princeton, he denounced American segregation and racism as a "disease of white people," joined the National Association for the Advancement of Colored People (NAACP), befriended singer and activist Paul Robeson, and offered to testify as a character witness for scholar W. E. B. Du Bois during the McCarthy era. In a May 1949 essay titled "Why Socialism?", published in the inaugural issue of Monthly Review, he argued for a planned socialist economy paired with democratic protections to overcome the economic anarchy and inequality of capitalism, while criticizing the totalitarian methods of the Soviet Union. A supporter of a Jewish cultural homeland in Palestine who helped Chaim Weizmann establish the Hebrew University of Jerusalem, Einstein favored peaceful binational coexistence with Arabs and criticized right-wing Jewish nationalist militia groups. Following Weizmann's death in November 1952, Israeli Prime Minister David Ben-Gurion offered Einstein the largely ceremonial presidency of Israel; Einstein declined, stating that he lacked the natural aptitude and experience to deal properly with people and official functions.

Regarding religion, Einstein rejected belief in a personal God who answers prayers or intervenes in human affairs, describing himself as an agnostic or a deeply religious nonbeliever. He stated that he believed in the pantheistic God of Baruch Spinoza, which reveals itself in the orderly harmony and lawful rational structure of the physical universe.

In 1948, surgeons discovered an abdominal aortic aneurysm in Einstein and reinforced the blood vessel by wrapping it in cellophane.³³³⁴ On 15 April 1955, after experiencing severe abdominal pain and internal bleeding caused by a rupture of the aneurysm, he was admitted to Princeton Hospital.³⁵ Even in the hospital, he requested his mathematical notes and worked on a draft speech commemorating the seventh anniversary of the State of Israel. He refused further surgical intervention, remarking that it was tasteless to prolong life artificially and that he wished to go elegantly when his time came. In the early morning of 18 April 1955, Einstein spoke a few words in German that the attending night nurse, Alberta Rozsel, could not understand, and died at 1:15 a.m. at the age of seventy-six.

In accordance with his wishes to avoid a public funeral or a burial site that might attract veneration, his body was cremated in Trenton, New Jersey, later that same afternoon, attended by twelve close family members and friends, and his ashes were scattered at an undisclosed location along the Delaware River. Before the cremation, Princeton Hospital pathologist Thomas Stoltz Harvey performed an autopsy and removed Einstein's brain without the prior permission of his family, preserving and sectioning it in hopes of identifying anatomical correlates of his intellect. Einstein bequeathed his personal archives, library, and intellectual property to the Hebrew University of Jerusalem.

Einstein's theoretical breakthroughs continue to underpin contemporary physics and technology. Both special and general relativity are required for the precise synchronization of satellite clocks in the Global Positioning System (GPS), where orbital velocities and weaker gravitational fields alter the passage of time relative to Earth's surface. His century-old predictions of gravitational waves and black holes were directly verified in the twenty-first century through the Laser Interferometer Gravitational-Wave Observatory (LIGO) detections beginning in 2015 and the Event Horizon Telescope imaging of supermassive black holes. Beyond science, his name and likeness became universally synonymous with genius, and in 1999 Time magazine named him the Person of the Century.