Sergei Tiviakov (Russian: Сергей Тивяков; born February 14, 1973 in Krasnodar, Soviet Union) is a naturalised Dutch chess Grandmaster.
Tiviakov won the Dutch Chess Championship in 2006 and 2007. In 2008, in Plovdiv, he won the European Individual Chess Championship with 8.5/11.
His first Olympiad appearance was for Russia at the Moscow event in 1994, when he took home a gold medal in celebration of the team's winning performance. He played for the Dutch team at each of the events held from 2000–2006, with an overall record of +14 −2 =33 (62.2%).
At the European Team Chess Championships, he has earned three gold medals (two team and one individual) for his contribution to the successful Dutch teams of 2001 (León) and 2005 (Gothenburg). At León, he registered a 77.8% score.
In 2009 he won the 13th Unive Tournament in Hoogeveen. In 2011 he came first in the Fagernes Chess Festival, in the 5th Leiden Chess Tournament and in the First Panama Chess Open.
He was awarded the Grandmaster title in 1991.