Steve Cantwell (born December 8th, 1986) is an American mixed martial artist currently fighting for the Ultimate Fighting Championship (UFC). He is also the final World Extreme Cagefighting (WEC) Light Heavyweight champion.

After acquring a 3-0 record in smaller shows, Cantwell made his WEC debut at WEC 26 in 2007 against Brian Stann, where he suffered a quick TKO loss. After two subsequent victories, Cantwell again faced Stann, now the Light Heavyweight champion, at WEC 35 and won by TKO in the second round. Shortly after Cantwell took the title, the WEC dropped both its Light Heavyweight and Middleweight divisions, making Cantwell the final WEC Light Heavyweight champion.

Later that year, Cantwell signed with the UFC, which is owned by the WEC's parent company Zuffa. Cantwell faced fellow UFC newcomer Razak Al-Hassan at UFC: Fight for the Troops and earned a technical submission victory by dislocating Al-Hassan's elbow in an armbar, causing Mario Yamasaki to stop the fight. Cantwell's celebration of the victory and post-fight comments sparked some criticism when he said, "I've been waiting so long to do that, you have no idea". He later apologized for his behavior.