Ernest Walton and John Cockroft (1932) were the first to split the nucleus in a completely controlled manner. This was under the direction of Rutherford (see below) who, whilst at the Cavendish laboratory, Cambridge had done so but not by entirely artificial means. In doing so Walton and Cockroft were also the first to verify Einstein's law: E = mc²
Lise Meitner is apparently the most correct answer. She was Austrian . She discovered it while living in Sweden during WWII. Meitner maintained contact with colleagues, which allowed her to partner in their work, but she ultimately came out with how to split the atom first (while in Sweden) and I believe that she was first to be published. She worked with Otto Hahn who never gave her credit for coming out with it first, because she was a woman and a Jew which didn't work well with added Nazi pressure.
Otto Hahn and Fritz Strassman (1938)
The below answer is not correct.
Lise Meitner was not the first to split the atom. However, she was the first to Theorize the Dumbbell concept. She worked with Otto Hahn for that experiment. They were good friends and colleagues. He was the first one to help her get out of Germany. (The Making of the Atomic Bomb by Richard Rhodes,)
Ernest Rutherford - A New Zealander - split the atom
The creator of modern atomic physics and forerunner of the nuclear age, Rutherford was one of the greatest scientists of the 20th century.
He was awarded the Nobel Prize in Chemistry in 1908 and a baronetcy in 1931.
In the words of Einstein, he was "a second Newton", the man who "tunneled into the very material of God": inventor, experimenter and Nelson farm boy.
Rutherford's strengths as a scientist are legion. A prolific, practical inventor and scientific theorist, his ideas were based on rigorous experimentation. He was one of the original "demo or die" scientists, turning conjecture into fact.
He attributed his willingness to experiment and find unorthodox solutions to his hardscrabble background in rural New Zealand: "We don't have the money, so we have to think".
Rutherford's Major Discoveries
Rutherford's three major discoveries shaped modern science, created nuclear physics and changed the way that we envisage the structure of the atom.
Rutherford's first discovery was that elements are not immutable, but can change their structure naturally, from heavy elements to slightly lighter. This led to him being awarded the Nobel Prize for Chemistry in 1908, at the age of 37, for his work on the transmutation of elements and the chemistry of radioactive material.
His second discovery, the nuclear model of the atom, became the basis for how we see the atom today: a tiny nucleus surrounded by orbiting electrons.
He built on this discovery for his third great achievement, the splitting of the atom, making him, as John Campbell says in his biography of Rutherford in The Dictionary of New Zealand Biography, "the world's first successful alchemist".
The first group to successfully initiate nuclear fission (splitting the atom) was a top-secret project called the Manhattan Project. It was initiated by a letter from Albert Einstein, and a whole group of top physicicists developed the program. The first person to actually split the atom was Enrico Fermi in 1942
Google The Manhattan Project, and you'll have your answer.
I was taught at school it was a New Zealander by the name of Earnest Rutherford who was working at Oxford University at the time. I think it was sometime in the 1920's.
*The work of Sir Rutherford and Misters Walton and Cockcroft are the first recorded, deliberate events that could be classified as 'splitting' an atom.
The Manhattan Project etc
As mentioned above, Rutherford, Walton and Cockcroft were the first to split the atom. The Manhatton project involved the development of a nuclear weapon. I believe Walton may have been asked to join a secret project, now known as The Manhatton Project, based on his earlier work. He may not have been told of the exact purpose of the project. In fact, they wouldn't have known of the possibilities of nuclear power at the time of splitting the atom. I'm no expert, but I believe the idea of a nuclear bomb came later. There were certain unknowns at the time of the initial splitting of the atom. It was later knowledge or ideas that proposed the concept of a nuclear weapon.
As an aside, Ernest Walton was Irish.
In April 1932 John Cockcroft and Ernest Walton split the atom
for the first time, at the Cavendish Laboratory in Cambridge in the
UK. Only weeks earlier, James Chadwick, also in Cambridge,
discovered the neutron. That same year, far away in California,
Carl Anderson discovered the positron while working on cosmic rays.
So 1932 was a veritable annus mirabilis in which experiments
discovered, and worked with, nucleons; exploited Albert Einstein's
relativity and energy-mass equivalence principle; took advantage of
the newly emerging quantum mechanics and its prediction of
"tunnelling" through potential barriers; and even verified the
existence of "antimatter" predicted by Paul Dirac's relativistic
quantum theory of the electron. It is hard to think of a more
significant year in the annals of science.
the Nazi regime in Germany first splitted the atom first but the decided not to use it to create an atomic bomb because they thought they would win the 2nd world war so then the Americans created the first atomic bomb
In 1932 Sir John Cockcroft and Ernest Walton were the first people to split an atom (causing a nuclear reaction) by using artificially accelerated particles.