Dietmar Gerhard Bartsch is a German politician who has served as co-chair of The Left parliamentary group in the Bundestag since 2015. Prior, he served as federal treasurer of The Left from 2006 to 2009 and federal managing officer from 2005 to 2010. He was a prominent member of The Left's predecessor party, the PDS, of which he served as treasurer from 1991 to 1997 and federal managing officer from 1997 to 2002.

The Left, commonly referred to as the Left Party, is a democratic socialist political party in Germany. The party was founded in 2007 as the result of the merger of the Party of Democratic Socialism (PDS) and Labour and Social Justice – The Electoral Alternative. Through the PDS, the party is the direct descendant of the Marxist–Leninist ruling party of former East Germany, that being the Socialist Unity Party of Germany (SED). Since 2022, The Left's co-chairpersons have been Janine Wissler and Martin Schirdewan. The party holds 28 seats out of 736 in the Bundestag, the federal legislature of Germany, having won 4.9% of votes cast in the 2021 German federal election. Its parliamentary group is the second-smallest of seven in the Bundestag, and is headed by parliamentary co-leaders Heidi Reichinnek and Sören Pellmann.