Daniel Castillo (born August 25, 1979) is an American retired mixed martial artist. A professional from 2007 until 2015, he competed in 22 bouts with both the Ultimate Fighting Championship (UFC) and the World Extreme Cagefighting (WEC).

Castillo began training MMA when he joined the wrestling team at his high school in suburban Sacramento. His vice principal, who was also the wrestling coach, told Castillo that if he joined the team, he would not call his mother after seeing Castillo constantly in trouble. Castillo claims he was scared his first day at practice, "I got the [expletive] kicked out of me that day, but after that, I wasn't nervous at wrestling practice ever." After leaving private school, Castillo graduated from Laguna Creek High School (Elk Grove, CA) and attended Menlo College; becoming an NAIA All American in 2004. His nickname "Last Call" was given to him in college due to his ability to perform well in his team's offseason morning runs despite having been up consuming massive amounts of alcohol until last call.

Castillo made his professional debut in November 2007, fighting twice in the month, winning both fights via first round submission. After going 3-0, Castillo signed to fight on the Palace Fighting Championship's seventh card. He fought Andy Salazar winning via submission due to his tough ground and pound. He won his fifth straight fight after defeating Strikeforce veteran, Isaiah Hill. With the win, Castillo was signed with the WEC.

Castillo made his debut against Donald Cerrone at WEC 34, replacing an injured Rich Crunkilton. Cerrone defeated Castillo via first round armbar submission.

Castillo then fought Rafael Dias at WEC 36, winning via TKO in the second round.

Four months later Castillo fought Phil Cardella at WEC 39. Castillo won the fight via split decision.

Castillo then defeated Ricardo Lamas, winning his third straight WEC fight.

Castillo was defeated by Shane Roller via third round submission at WEC 44.