August Jonathan Karlin (born 9 June 2003) is a Swedish professional footballer who plays as a central midfielder for Ettan Södra club BK Olympic.
Karlin began his career with Kyrkheddinge IF before moving to Malmö FF at 11 years old. While progressing through the academy, he was re-trained into a central midfielder after previously playing as an attacker. On 22 December 2021, Karlin signed a professional contract with Malmö FF. He was subsequently loaned out to BK Olympic for the 2022 season. Before the 2023 season, Karlin was sent on another loan, this time to Superettan club Jönköpings Södra.
On 31 January 2024, Karlin left Malmö FF on a permanent deal to Eliteserien club Lillestrøm SK. There he was reunited with his previous youth coaches Andreas Georgson and Robin Asterhed, who had just been hired as head coach and assistant coach, respectively, by the Norwegian first tier club. Karlin played 8 league games during the season but following the club's degradation to the second tier, Karlin's contract was terminated by mutual consent.
After a year in Norway, Karlin returned to BK Olympic for the 2025 season.
Karlin is a youth international for Sweden.
Karlin's father is of Slovenian descent.