Dimitrios Mastrovasilis (Greek: Δημήτριος Μαστροβασίλης; born 12 June 1983) is a Greek chess Grandmaster.
He took the silver medal in the European under-18 championship of 2000. In 2003 Mastrovasilis won the 1st Mediterranean Junior Championship in Ajelat, Libya. The following year he tied for 1st–2nd with Kiril Georgiev at Topola. Mastrovasilis competed in the FIDE World Chess Championship 2004, where he was eliminated in the first round by Konstantin Sakaev. In 2007 he tied for 2nd–7th with Kiril Georgiev, Vadim Malakhatko, Mircea Parligras, Hristos Banikas and Dmitry Svetushkin in the Acropolis International Chess Tournament. In 2012 he won the Artemis Cup in Leros.
Mastrovasilis played for Greece in the Chess Olympiads of 2000, 2004, 2006, 2008, 2010, 2012 and 2014.
His brother is Grandmaster Athanasios Mastrovasilis.