|Born:||June 7, 1997|
Newport Beach, California
|Height:||6 ft 5 in (1.96 m)|
|Weight:||225 lb (102 kg)|
|High school:||Santa Margarita Catholic|
(Rancho Santa Margarita, California)
Mississippi State (2020)
|* Offseason and/or practice squad member only|
|Career highlights and awards|
|Career NFL statistics|
|Player stats at NFL.com|
Kevin Richard "K. J." Costello (born June 7, 1997) is an American football quarterback who is a free agent. He played college football for the Stanford Cardinal and the Mississippi State Bulldogs.
Costello attended Santa Margarita Catholic High School in Rancho Santa Margarita, California. During his high school football career, he passed for a school record 8,222 yards and 62 passing touchdowns. Rated as one of the top quarterback recruits in his class, Costello committed to Stanford University to play college football.
Costello redshirted his first year at Stanford in 2016. He entered 2017 as a backup to Keller Chryst, but made his first career start against UCLA after Chryst was injured. Costello returned as the backup after the game; however, he took over as the starter prior to the eighth game of the season. He remained the starter throughout the rest of the season and finished with 1,573 passing yards, 14 touchdowns and four interceptions.
On December 18, 2019, Costello entered the transfer portal. On February 3, 2020, Costello announced he would be transferring to Mississippi State.
Costello made his first start for Mississippi State on September 26, 2020, where he broke the SEC record for passing yards in a single game with 623 yards in a 44–34 victory over the defending national champion, LSU.
On August 1, 2021, Costello signed with the Los Angeles Chargers after going undrafted in the 2021 NFL Draft. He was waived on August 17.