Ryan Bader (/ˈbeɪdər/ BAY-dər; born June 7, 1983) is an American mixed martial artist and actor who competes in the Heavyweight division of RIZIN. He previously competed for Bellator MMA where he was the Bellator Heavyweight Champion, and still holds the record for the longest continuous winning streak of any Bellator Champion. He is also the former Bellator Light Heavyweight Champion, and the winner of the 2018 Bellator Heavyweight World Grand Prix Tournament. At Bellator 214, Bader became the first fighter in Bellator history to become champion in two weight divisions simultaneously. Prior to signing with Bellator, Bader competed for the Ultimate Fighting Championship (UFC) in the Light Heavyweight division and he was a cast member and winner of The Ultimate Fighter: Team Nogueira vs. Team Mir. In the 2025 movie The Smashing Machine, Bader plays MMA fighter Mark Coleman.

Ryan Bader was born in Reno, Nevada and started wrestling at the age of seven. He entered mixed martial arts after a successful career in amateur wrestling. He attended Robert McQueen High School in Reno, where he won two Nevada state championships and was ranked as high as fourth in the country for wrestling. In football, Bader was the 2001 Nevada Defensive Player of the Year and helped the McQueen Lancers win the Nevada state championship title.

Bader attended Arizona State University on a wrestling scholarship, where he was college teammates with former UFC Heavyweight Champion Cain Velasquez and CB Dollaway. While attending ASU, Bader was a three-time Pac-10 Champion, winning titles in 2003, 2004, and 2006. He was also a two-time NCAA All-American, placing fourth in 2004 as a sophomore and seventh in 2006 as a senior at the NCAA national tournament. From 2003 to 2005, Bader compiled a collegiate wrestling record of 88 wins and 34 losses. He began training at Arizona Combat Sports in early 2007.

Bader's UFC career began as a contestant on season 8 of The Ultimate Fighter. Bader, the first light heavyweight selected by coach Antônio Rodrigo Nogueira, went on to win his first three fights on the show to fight with Vinicius Magalhães on December 13, 2008, at The Ultimate Fighter 8 Finale.

At the finale, Bader defeated Magalhães by way of a quick, first-round knockout, earning the title of "The Ultimate Fighter" and winning the traditional "six-figure UFC contract". An overhand right dropped Magalhães, and Bader followed up with strikes on the ground to take the win, less than halfway through the first round.

Bader's first post-TUF fight was at UFC Fight Night 18 against Carmelo Marrero, whom he defeated via unanimous decision, scoring 30–27 on all three judges' scorecards. During the match, Bader tore his medial collateral ligament and posterior cruciate ligament, which kept him sidelined until the next fall.

Shortly after the Marrero fight, Bader appeared alongside fellow Ultimate Fighter 8 winner Efrain Escudero in the UFC's sixth video game, UFC 2009 Undisputed. He and Escudero were available through a special code obtained by pre-ordering the game from GameStop. On September 10, 2009, he and Escudero were made available for download on PlayStation Network and Xbox 360 Marketplace.

Bader returned against Eric Schafer on October 24, 2009, at UFC 104. The fight was mainly dominated by Bader, who scored with a powerful attack of combinations standing and controlled the grappling, en route a unanimous decision victory (30–27, 29–26, and 30–27).