Fritz Zwicky was born in Varna, Bulgaria, to a Swiss father. His father, Fridolin Zwicky (b. 1868), was a prominent industrialist in the Bulgarian city and also served as ambassador of Norway in Varna (1908 – 1933). The Zwicky House in Varna was designed and built by Fridolin Zwicky. Fritz's mother, Franziska Vrček (b. 1871), was an ethnic Czech of the Austro - Hungarian Empire. Fritz was the oldest of the Zwicky family's three children: he had a younger brother named Rudolf and a sister called Leoni. Fritz's mother died in Varna in 1927 and his father Fridolin remained in Bulgaria until 1945, when he returned to Switzerland. His sister Leoni married to a Bulgarian from Varna and spent her entire life in the city.

In 1904, at the age of six, Fritz was sent to his grandparents in Glarus, Switzerland, "the Zwicky's ancestral Swiss canton, to study commerce." His interests shifted to math and physics and he received an advanced education in mathematics and experimental physics at the Swiss Federal Institute of Technology, located in Zürich, Switzerland. In 1925, he emigrated to the United States to work with Robert Millikan at California Institute of Technology (Caltech) after receiving the "international fellowship from the Rockefeller Foundation."

He was responsible for positing numerous cosmological theories that have a profound impact on understanding of our universe today. He was appointed Professor of Astronomy at Caltech in 1942 and also worked as a research director / consultant for Aerojet Engineering Corporation (1943 – 1961) and staff member of Mount Wilson Observatory and Palomar Observatory for most of his career. He developed some of the earliest jet engines and holds over 50 patents, many in jet propulsion, and is the inventor of the Underwater Jet (TIME March 14, 1949), the Two Piece Jet Thrust Motor and Inverted Hydro Pulse.

In April 1932, Fritz Zwicky married Dorothy Vernon Gates, the daughter of a prominent local family and Senator Egbert Gates. Her money was instrumental in the funding of the Palomar Observatory during the Great Depression. Nicholas Roosevelt, cousin of President Theodore Roosevelt, was his brother - in - law by marriage to Tirzah Gates. Zwicky and Dorothy divorced amicably in 1941. In 1947 Zwicky was married in Switzerland to Anna Margaritha Zurcher, and they had three daughters, Margrit, Franziska, and Barbarina. Three grandchildren were born after his passing away. The Zwicky Museum at the Landesbibliothek, Glarus, houses many of his papers and scientific works, and the Fritz Zwicky Stiftung (Foundation) in Switzerland carries on his ideas relating to "morphological analysis". Zwicky died in Pasadena on February 8, 1974 and was buried in Mollis, Switzerland.

Fritz Zwicky was a prolific scientist and made important contributions in many areas of astronomy.

Together with colleague Walter Baade, Zwicky pioneered and promoted the use of the first Schmidt telescopes used in a mountain top observatory in 1935. He hand carried the Schmidt lens from Germany, which had been polished by the optician, Bernard Schmidt. In 1934 he and Baade coined the term "supernova" and hypothesized that they were the transition of normal stars into neutron stars, as well as the origin of cosmic rays. It was a prescient insight that had tremendous impact in determining the size and age of the universe in subsequent decades.

In support of this hypothesis, Zwicky started hunting for supernovae, and found a total of 120 by himself (and one more, SN 1963J, in concert with Paul Wild) over a stretch of 52 years (SN 1921B through SN 1973K), a record which still stands as of 2006 (the current runner up is Jean Mueller, with 98 discoveries and 9 co-discoveries).

In 1938, Zwicky's colleague Walter Baade proposed using supernovae as standard candles to estimate distances in deep space. Because light curves of many type-Ia supernovae show a common peak luminosity, they establish a cosmological distance scale by a well known intrinsic brightness.

Distant Type Ia supernovae show a nonlinear Hubble relationship, which scientists have explained in terms of an acceleration in the expansion rate for the universe.

In 1937, Zwicky posited that galaxy clusters could act as gravitational lenses by the previously discovered Einstein effect. It was not until 1979 that this effect was confirmed by observation of the so-called "Twin Quasar" Q0957+561.

While examining the Coma galaxy cluster in 1933, Zwicky was the first to use the virial theorem to infer the existence of unseen matter, what is now called dark matter. He was able to infer the average mass of galaxies within the cluster, and obtained a value about 160 times greater than expected from their luminosity, and proposed that most of the matter was dark. The same calculation today shows a smaller factor, based on greater values for the mass of luminous material; but it is still clear that the great majority of matter is dark.

When Edwin Hubble discovered a linear relationship between the distance to a galaxy and its redshift expressed as a velocity, Zwicky immediately speculated that the effect was due not to motions of the galaxy, but to some inexplicable phenomenon that mysteriously caused photons to lose energy as they traveled through space. He considered the most likely candidate process to be a drag effect in which photons transfer momentum to surrounding masses through gravitational interactions; and proposed that an attempt be made to put this effect on a sound theoretical footing with general relativity. He also considered and rejected explanations involving interactions with free electrons, or the expansion of space.

Zwicky was skeptical of the expansion of space in 1929, because the rates measured at that time seemed too large. It was not until 1956 that Walter Baade corrected the distance scale based on Cepheid variable stars, and ushered in the first accurate measures of the expansion rate. Cosmological redshift is now conventionally understood to be a consequence of the expansion of space; a feature of Big Bang cosmology.

Zwicky developed a generalised form of morphological analysis, which is a method for systematically structuring and investigating the total set of relationships contained in multi-dimensional, usually non quantifiable, problem complexes. He wrote a book on the subject in 1969, and claimed that he made many of his discoveries using this method.

Zwicky devoted considerable time to the search for galaxies and the production of catalogs. From 1961 to 1968 he and his colleagues published a comprehensive six volume Catalogue of galaxies and of clusters of galaxies. They were all published in Pasadena, by the California Institute of Technology.

Galaxies in the original catalog are called Zwicky galaxies, and the catalog is still maintained and updated today. Zwicky with his wife Margaritha also produced an important catalog of compact galaxies, sometimes called simply The Red Book.

Zwicky was an extraordinarily original thinker, and his contemporaries frequently had no way of knowing which of his ideas would work out and which would not. In a retrospective look at Zwicky's life and work, Stephen Maurer said:

When researchers talk about neutron stars, dark matter, and gravitational lenses, they all start the same way: “Zwicky noticed this problem in the 1930s. Back then, nobody listened . . .”

He is celebrated for the discovery of neutron stars. He also went on to consider nuclear goblins, which he proposed as "a body of nuclear density ... only stable under sufficient external pressure within a massive and dense star". He considered that goblins could move within a star, and explode violently as they reach less dense regions towards the star's surface, and serve to explain eruptive phenomena, such as flare stars. This idea has never caught on.

An anecdote often told of Zwicky concerns an informal experiment to see if he could reduce problems with turbulence hindering an observation session one night at Mount Wilson observatory. He told his assistant to fire a gun out through the telescope slit, in the hope it would help to smooth out the turbulence. No effect was noticed, but the event shows the kind of lateral thinking for which Zwicky was famous.

He was also very proud of his work in producing the first artificial meteors. He placed explosive charges in the nose cone of a V2 rocket, to be detonated at high altitude and fire high velocity pellets of metal through the atmosphere. The first attempts appeared to be failures, and Zwicky sought to try again with the Aerobee rocket. His requests were denied, until the Soviet Union launched Sputnik 1. Twelve days later, on October 16, 1957, Zwicky launched his experiment on the Aerobee, and successfully fired pellets visible from the Mount Palomar observatory. It is thought that one of these pellets may have escaped the gravitational pull of the Earth and become the first object launched into a solar orbit.

Zwicky also considered the possibility of rearranging the universe to our own liking. In a lecture in 1948 he spoke of changing planets, or relocating them within the solar system. In the 1960s he even considered how the whole solar system might be moved like a giant spaceship to travel to other stars. He considered this might be achieved by firing pellets into the Sun to produce asymmetrical fusion explosions, and by this means he thought that the star Alpha Centauri might be reached within 2500 years.

Although Zwicky had difficulties in personal relationships with his peers and had few formal students, he was a generous humanitarian with a great concern for wider society. These two sides of his nature came together in the aftermath of the second World War, when Zwicky worked hard to collect tons of books on astronomy and other topics, and shipped them to the war ravaged scientific libraries in Europe and Asia.

He also had a longstanding involvement with the charitable Pestalozzi Foundation of America, supporting orphanages. Zwicky received their gold medal in 1955, in recognition of his services.

Zwicky loved the mountains, and was an accomplished alpine climber.

He was a strong critic of organized religion but not individual faith, and of nationalism, and was critical of political posturing by all sides in the Middle East, and of the use of nuclear weapons in World War II. He considered that hope for the world lay with free people of good will who work together as needed, without institutions or permanent organizations.

In 1949, Truman awarded Zwicky the Presidential Medal of Freedom, for work on rocket propulsion during World War II. In 1968, Zwicky was made professor emeritus at California Institute of Technology.

In 1972, Zwicky was awarded the Gold Medal of the Royal Astronomical Society, their most prestigious award, for "distinguished contributions to astronomy and cosmology". This award noted in particular his work on neutron stars, dark matter, and cataloging of galaxies.

The asteroid 1803 Zwicky and the lunar crater Zwicky are both named in his honour.