Tarjei Bø (born 29 July 1988) is a Norwegian professional biathlete. Bø debuted in the Biathlon World Cup on 26 March 2009 in Khanty-Mansiysk, Russia, and won his first World Cup victory on 10 December 2010. In the 2010 Winter Olympics he earned his first gold medal in the 4 × 7.5 km biathlon relay. On 10 December 2010 he won the sprint race in Hochfilzen, earning his first world cup victory. He also won the following pursuit race and anchored the winning relay team. Bø is the older brother of biathlete Johannes Thingnes Bø.
He won the overall 2010/11 biathlon World Cup. He finished five points ahead of his teammate Emil Hegle Svendsen.
At his first Junior World Championships in 2006 in Presque Isle, Maine, United States, Bø claimed the gold medal in the individual discipline, and the silver medal in the pursuit discipline. A year later in Martell-Val Martello, Italy, Bø again claimed the silver medal in the pursuit discipline, and was part of the Norwegian relay team that won the silver medal. The 2009 Junior World Championships in Canmore, Canada began in disappointment: Bø finished as number 23 in the individual discipline with a total of five shooting errors. However, Bø would eventually claim the bronze medal in both the pursuit and sprint disciplines. During the 2009 European Championships in Ufa, Russia, Bø was the most successful biathlete, and claimed the gold medal in all four races he entered (individual, sprint, pursuit and relay). At the World Cup finals in Khanty Mansiysk, Russia, Bø made his debut in the Biathlon World Cup on 26 March 2009, finishing 61st.