Marshall Eriksen (born 1978)has been Ted Mosby's best friend since 1996, when the two met at Wesleyan University as undergraduates. He is currently married to the love of his life and fellow Wesleyan alum, Lily Aldrin. Brought up in the tightly-knit community of St. Cloud, Minnesota, Marshall's inherent kindness makes him the most compassionate member of the gang. He has recently quit his job as a corporate lawyer at Goliath National Bank to pursue his dream of saving the world through environmental law. As of Challenge Accepted, Lily is found to be pregnant, and she gives birth in The Magician's Code - Part One to a boy named Marvin W. Eriksen. In Daisy, it is revealed that Lily is pregnant again and that she gives birth to their first daughter, Daisy Eriksen in February 2014.

Marshall was born and raised in St. Cloud, Minnesota. He became very close to his parents and was taught manners by them. He is also close to his brothers.

Marshall met Ted Mosby and Lily Aldrin on the first day of their freshman year at Wesleyan University. Marshall graduated with Ted from Wesleyan in 2000, as implied in How I Met Everyone Else. He began law school at Columbia in 2004, he managed a structure in between leaving Wesleyan and starting at Columbia.

Marshall is very polite since he has grown up in Minnesota. He is loving and caring and confident and extremely emotional, which he often gets teased of by the gang. He is very passionate about what he does, and cares deeply for his family and friends.