Mark Alan Ruffalo (/ˈrʌfəloʊ/; born November 22, 1967) is an American actor and producer who began his career in the late 1980s and first gained recognition for his work in Kenneth Lonergan's play This Is Our Youth (1996) and drama film You Can Count on Me (2000). He went on to star in the romantic comedies 13 Going on 30 (2004) and Just like Heaven (2005), and the thrillers In the Cut (2003), Zodiac (2007), and Shutter Island (2010). He received a Tony Award nomination for his supporting role in the Broadway revival of Awake and Sing! in 2006. Ruffalo has gained international recognition for playing Bruce Banner/Hulk in the Marvel Cinematic Universe, beginning with The Avengers (2012).

Ruffalo earned a record-tying four nominations for the Academy Award for Best Supporting Actor for playing a sperm donor in The Kids Are All Right (2010), Dave Schultz in Foxcatcher (2014), Michael Rezendes in Spotlight (2015), and a debauched lawyer in Poor Things (2023). He won a Screen Actors Guild Award for Best Actor for playing a gay activist in the television drama film The Normal Heart (2015) and a Primetime Emmy Award for Outstanding Lead Actor for his dual role as identical twins in the miniseries I Know This Much Is True (2020).