Rob Wiethoff is an American actor and voice actor. He is best known for portraying John Marston in the 2010 video game Red Dead Redemption, its expansion Undead Nightmare, and the 2018 prequel Red Dead Redemption 2.

For his role in Red Dead Redemption, Wiethoff won Outstanding Character Performance at the 14th Annual Interactive Achievement Awards.

He was nominated for Best Performance by a Human Male at the 2010 Spike Video Game Awards, where John was also nominated for Character of the Year. In 2013, Complex named Wiethoff’s performance as one of the best in a video game, praising the growth of the character.