Unless I screwed up my research, it's Aleksandar Matanović from Serbia (aged 91). GM Nikolai Krogius is also 91, but a bit younger.
en.wikipedia.org/wiki/Aleksandar_Matanovi%C4%87en.wikipedia.org/wiki/Nikolai_KrogiusYuri Averbakh
100 years old
<Comment deleted by user>
@Kriegerkind2020In Memoriam: Yuri Averbakh, 1922-2022
.
.
.
Erratum: Enver Bukić *died* in 2017, according to his profile on
ChessGames.comP.S.: GM Matanović has contributed to Opening Theory (!) – there's something called "Matanović Attack" in the Scheveningen Sicilian.
Source:
www.chess.com/openings/Sicilian-Defense-Open-Scheveningen-Matanovic-Attack