Jónína Þórdís Karlsdóttir (born 23 November 1999) is an Icelandic basketball player who plays for Ármann.
After playing for Valur and Stjarnan between 2015 and 2017 in Úrvalsdeild kvenna, she stepped away from basketball. In 2020, she was a key part of re-establishing the Ármann's senior women's team. During the 2020–2021 season, she averaged 20.2 points, 9.5 rebounds and 4.3 assists per game. In 2025, she guided the team to promotion to the Úrvalsdeild for the first time since 1960. Following the season, she was named the 1. deild domestic player of the year for the third time.