Nicholas Clayton Mullens (born March 21, 1995) is an American professional football quarterback for the Jacksonville Jaguars of the National Football League (NFL). He played college football for the Southern Miss Golden Eagles, where he surpassed Brett Favre's single-season school records for passing yardage (4,476) and touchdown passes (38). Mullens was signed by the San Francisco 49ers as an undrafted free agent in 2018 and has also been a member of the Philadelphia Eagles, Cleveland Browns, Las Vegas Raiders, and Minnesota Vikings.

Mullens was born to Suzanne and Mark Mullens on March 21, 1995, in Little Rock, Arkansas and grew up in Hoover, Alabama, a suburb of Birmingham. He is the grandson of Ernie Tabor, who pitched in the Philadelphia Phillies minor league system in the 1950s. Mullens' uncle, Scott Tabor, pitched for the Arkansas Razorbacks baseball team, and holds the school record for most career wins; he also pitched professionally in the minor leagues. Mullens graduated from Spain Park High School in Hoover.

Mullens played football for Spain Park, emerging as the team's starting quarterback. As a senior in 2012, he threw for 3,649 yards and 40 touchdowns against only seven interceptions en route to winning the 2012 Gatorade Player of the Year award for the state of Alabama. Mullens had totaled 8,605 career passing yards, finishing his high school career with the seventh most passing yards in AHSAA history.

After originally verbally committing to attend the University of Alabama at Birmingham, Mullens changed course on national signing day following a last-minute visit to the University of Southern Mississippi, signing instead with the Golden Eagles.

After starting the 2013 season with a 0–6 record, in an 18-game losing streak, Southern Miss head coach Todd Monken inserted true freshman Mullens as a starter for the home game against the North Texas Mean Green. However, the young team was overmatched by North Texas, suffering a 55–14 loss where Mullens went 12-for-31 passing for 210 yards and a touchdown, while suffering three interceptions and a lost fumble.

In his second collegiate game, a loss to Marshall, Mullens became the first true freshman starting quarterback in Southern Miss history to pass for more than 300 yards in a single game, a feat never accomplished during his freshman year by the school's most famous football alumnus, Brett Favre.

On November 30, 2013, Mullens played a key role in helping Southern Miss end its losing streak at 23 games with a five-touchdown performance against the University of Alabama-Birmingham, which also happened to be the college that he originally committed to.

Mullens passed for 1,776 yards as a freshman in 2013.