Career
He plays primarily at the shooting guard position, but he can also play point guard if needed. Marius started his professional basketball career in Klaipėda, NKL team Nafta-Uni-Laivitė in 2003. Before that he played in Lithuanian Pupil Basketball League (MKL) for V.Chomičius basketball school.
Year After he joined British Columbia Sūduva, and in 2009 January he left club and joined Latvian"s basketball team ASK Group (a software company) Riga.
In following season he averaged 16.9 points, 3.9 assists and 3.3 rebounds After the season he joined UJAP Quimper, playing in Ligue Nationale de Basketball Second Division in France. In UJAP he averaged 14.1 points, 1.6 assists and 2.6 rebounds.
In June, 2011 he returned to British Columbia Neptūnas and signed a two year contract with the team In July 2014, he moved to Romania and signed a one-year deal with Christlich Soziale Union (Christian Social Union) Asesoft Ploiești.
In June, 2015 he signed two-years (1+1) deal with Lietuvos rytas Vilnius.
In 2015 Runkauskas was included into the Lithuania men"s national basketball team head coach Jonas Kazlauskas extended candidates list. He also participated in the national team training camp, but was released on August 16. 2006 - NKL Runner-up.