Kristján Örn Kristjánsson, better known as "Donni", started playing at an early age for Fjölnir, the local team in Grafarvogur, Reykjavík. He made the "first team" in Fjölnir in 2013.
In 2018, Kristján Örn joined ÍBV, a team located in Vestmannaeyjar, an island group south of Iceland. During a successful two-year run with ÍBV, he caught the attention of French team Pays d’Aix Université Club Handball, PAUC.
Kristján has played a pivotal role with PAUC, emerging as the top scorer for the team in the 2020/21 season.
The upcoming EHF Euro 2024 won't be Kristján's first big tournament, as he already represented the national team at the World Championship in 2021 and the European Championship in 2022.