Vejle Born in
Copenhagen, Provstgaard moved to
Vejle at the age of four and joined
Vejle Boldklub from Bredballe IF at under-13 level. He progressed through the club's youth system and was first named in the senior matchday squad on 7 October 2020 for a
Danish Cup match against
Hobro, although he remained an unused substitute. In December 2020, Provstgaard suffered a serious knee injury in an under-19 match, which required surgery and kept him out for several months. Despite the injury, Vejle announced on 7 June 2021 that he had signed a new contract running until June 2024, effective from 1 January 2022, when he was also due to become a permanent member of the first-team squad. Provstgaard later said that the rehabilitation period had strengthened him both physically and mentally. On 27 May 2022, he signed a further contract extension until June 2026.
Lazio On 3 February 2025, Provstgaard joined Italian
Serie A club
Lazio on a contract reported to run until June 2029. He made his Serie A debut on 6 April 2025, coming on as a substitute for
Samuel Gigot in the 68th minute of a 1–0 away victory over
Atalanta at the
Gewiss Stadium in
Bergamo, with compatriot
Gustav Isaksen scoring the only goal. Head coach
Marco Baroni said afterwards that "the new players also made an important contribution today", though Provstgaard made little further impression in the second half of the
2024–25 season, finishing with 33 minutes across two substitute appearances in total. When
Maurizio Sarri was appointed head coach for the
2025–26 season, Provstgaard's position at the club changed markedly. He featured consistently during pre-season and was selected to start Lazio's opening league fixture on 24 August 2025 away at
Como, partnering
Mario Gila in central defence while
Alessio Romagnoli served a suspension. Among his most prominent performances was a home fixture against
Fiorentina, in which he recorded 128 touches and completed 117 passes with just six errors, statistics noted by the
Corriere dello Sport as indicative of an unusually authoritative display for a player of his age and experience. He started the 2–0 away victory over
Napoli at the
Stadio Diego Armando Maradona on 18 April 2026, a result in which Napoli registered no shots on target—a statistic not recorded against them at home in 21 years of Serie A football. Speaking to Lazio's official channel after the match, Provstgaard reflected on his development under Sarri: "I am very happy with my growth at Lazio, especially this year with the coach. I am learning so many things—also from Gila and Romagnoli. I feel ready to be a starter, but that must not be my choice; it must be the coach's." ==International career==