Istvan Abonyi (1886-1942) was a Hungarian master. He was born and died in Budapest.
In 1912, he played the Abonyi Gambit (1.Nf3 d5 2.e4) for the first time.
In 1916, he played the Budapest Gambit (1.a3 Nf6 2.b3 e5) against the Dutch surgeon Johannes Esser in Budapest. Abonyi, along with Zsigmond Barasz and Gyula Beyer developed the Budapest Gambit.
In 1922 he published analysis on the Abonyi Variation of the Budapest Defense (1.d4 Nf6 2.c4 e5 3.dxe5 Ng4 4.e4 Nxd5 5.f4 Nec6) in Deutsches Wochenschach. He was one of the 15 founders of FIDE in 1924.
On January 21-22, 1928 in Budapest, he played 300 opponents on 105 boards, scoring 79 wins, 6 losses, and 20 draws.
He was President of the Correspondence Chess Federation between 1935 and 1939.
For many years, he was President of the Hungarian Chess Federation and edited the Hungarian chess magazine Magyar Sakkvilag (Hungarian Chessworld).