Philip Hauge Abelson (April 27, 1913 – August 1, 2004) was an American physicist, scientific editor and science writer. Trained as a nuclear physicist, he co-discovered the element neptunium, worked on isotope separation in the Manhattan Project, and wrote the first study of nuclear marine propulsion for submarines. He later worked on a broad range of scientific topics and related public policy, including organic geochemistry, paleobiology and energy policy.

Abelson served as editor-in-chief of the journal Science from 1962–84, president of the Carnegie Institution of Washington from 1971–78, and president of the American Geophysical Union from 1972-74. His frequent editorials in Science, both during and after his term as editor, became known for their strident and thought-provoking views. A collection of 100 of his editorials was published as a book, entitled Enough of Pessimism. He may have been the original source of the phrase 'extraordinary claims require extraordinary evidence'.

Abelson was born on April 27, 1913, in Tacoma, Washington, to Norwegian immigrant parents. He attended Washington State University, where he received degrees in chemistry and physics, and the University of California, Berkeley (UC Berkeley), where he earned his PhD in nuclear physics. As a young physicist, he worked for Ernest Lawrence at the UC Berkeley. He was among the first American scientists to verify nuclear fission in an article submitted to Physical Review in February 1939. From 1939 until 1941, he worked as an assistant physicist at the Carnegie Institution in Washington, D.C. It was while he was here that he worked on a substance that emitted beta rays and was produced by irradiation of uranium with neutrons. After he collaborated with the Nobel Prize laureate Luis Alvarez they isolated the material, and became the co-discoverer of neptunium on 8 June 1940 with Edwin McMillan. McMillan was awarded the Nobel Prize for this discovery among other elements.

Abelson was a key contributor to the Manhattan Project during World War II, while working with the Naval Research Laboratory. Although he was not formally associated with the atom bomb project, the liquid thermal diffusion isotope separation technique that he invented at the Philadelphia Navy Yard was used in the S-50 plant in Oak Ridge, Tennessee, and proved a critical step in creating the large amount of nuclear fuel required for building atomic bombs.

After the war, he turned his attention under the guidance of Ross Gunn to applying nuclear power to naval propulsion. While not written at an engineering-design level, he wrote the first physics report detailing how a nuclear reactor could be installed in a submarine, providing both propulsion and electrical power. His report anticipated the nuclear submarine's role as a missile platform. This concept was later supported by Admiral Hyman G. Rickover and others. Under Rickover, the concept became reality in the form of USS Nautilus, the world's first nuclear submarine.

In 1946, he returned to work at the Carnegie Institution, which published his report "Atomic Energy Submarine," in March of that year. From 1953 until 1971 he served as the director of the Carnegie Institution of Washington's Geophysical Laboratory, and as president from 1971 to 1978, and as a trustee from 1978 on. From 1962 to 1984 he was editor of Science, one of the most prestigious academic journals, and served as its acting executive officer in 1974, 1975 and 1984. From 1972 until 1974 he served as the president of the American Geophysical Union.

Abelson was outspoken and well known for his opinions on science. In a 1964 editorial published in Science magazine, Abelson identified overspecialization in science as a form of bigotry. He outlined his view that the pressure towards specialization beginning in undergraduate study and intensifying in PhD programs leads students to believe that their area of specialization is the most important, even to the extreme view that other intellectual pursuits are worthless. He reasoned that such overspecialization led to obsolescence of one's work, often through a focus on trivial aspects of a field, and that avoidance of such bigotry was essential to guiding the direction of one's work.

In a 1965 article he described his work in paleobiology and reported evidence of amino acids recovered from fossils hundreds of millions of years in age and fatty acids in rocks dating over a billion years old. He estimated that based on his experiments alanine would be stable for billions of years.