user4418: In September 2022 19 year old Hans Niemann beat Magnus Carlsen in the Sinquefield Cup.
On the 19th January 2023 18 year old Nodirbek Abdusattorov beat Magnus Carlsen in the Tata Steel tournament.
Is Abdusattorov the youngest player to beat a reigning world champion in a classical (i.e. not rapid or blitz) over-the-board game?

user14079: I have not identified the record with certainty, but here are some young winners of World Champions in classical chess:

N.Abdusattorov, 18y 4m 1d, vs Carlsen in Wijk aan Zee 2023

V.Kramnik, 18y 8m 11d, vs Kasparov in Linares 1994.

A.Esipenko, 18y 9m 17d, vs Carlsen in Wijk aan Zee 2021

T.Radjabov, 18y 11m 10d, vs Topalov in Linares 2006



4418: <p>In September 2022 19 year old <a href="https://en.wikipedia.org/wiki/Carlsen%E2%80%93Niemann_controversy" rel="nofollow noreferrer">Hans Niemann beat Magnus Carlsen in the Sinquefield Cup</a>.</p>
<p>On the 19th January 2023 18 year old <a href="https://twitter.com/ChesscomLive/status/1616143570276319232" rel="nofollow noreferrer">Nodirbek Abdusattorov beat Magnus Carlsen in the Tata Steel tournament</a>.</p>
<p>Is Abdusattorov the youngest player to beat a reigning world champion in a classical (i.e. not rapid or blitz) over-the-board game?</p>
 14079: <p>I have not identified the record with certainty, but here are some young winners of World Champions in classical chess:</p>
<ul>
<li><p>N.Abdusattorov, 18y 4m 1d, <a href="https://www.chessgames.com/perl/chessgame?gid=2457584" rel="nofollow noreferrer">vs</a> Carlsen in Wijk aan Zee 2023</p>
</li>
<li><p>V.Kramnik, 18y 8m 11d, <a href="https://www.chessgames.com/perl/chessgame?gid=1070706" rel="nofollow noreferrer">vs</a> Kasparov in Linares 1994.</p>
</li>
<li><p>A.Esipenko, 18y 9m 17d, <a href="https://www.chessgames.com/perl/chessgame?gid=2021289" rel="nofollow noreferrer">vs</a> Carlsen in Wijk aan Zee 2021</p>
</li>
<li><p>T.Radjabov, 18y 11m 10d, <a href="https://www.chessgames.com/perl/chessgame?gid=1397157" rel="nofollow noreferrer">vs</a> Topalov in Linares 2006</p>
</li>
</ul>
