Jóhann Hjartarson (born 8 February 1963) is an Icelandic chess grandmaster and lawyer.

Since 1998, Johann has been the general counsel and secretary of the Icelandic biotechnology company deCODE genetics, a subsidiary of Amgen.

Jóhann competed in the FIDE world championship held with the knock-out format in 1998 and 2004.

With this latter win (in which he edged out Nils Grandelius on tiebreak score),[7][8] Jóhann qualified to play in the FIDE World Cup 2017.

Playing at the European Chess Club Cup, he won the gold medal with German team Bayern Munich in 1992.