Algirdas Sysas (born 5 March 1954 in Vilnius, Lithuania) is a Lithuanian social democratic politician and trade unionist.

Prior to political activities, Sysas was the leader and initiator of the independent Lithuanian trade unions.

Sysas started his professional career as a worker at a radio measurement device factory.

Sysas belongs to the inter-parliamentary relations groups with Austria, China, France, Germany, Japan, North European countries (Denmark, Finland, Iceland, Norway, Sweden), Poland and Romania.

He has been adept at orienteering since the 1970s, participating in numerous local, national and international competitions.