Bartosz Piotr Grzelak (born 2 November 1978) is a Swedish football manager who currently serves as the head coach of Nemzeti Bajnokság I club Újpest FC.
In June 2017 he joined as assistant manager to Rikard Norling in Allsvenskan side AIK.
In December 2018 he was appointed as assistant manager to the Sweden national under-21 football team.
FC Slovácko in the 2022–23 UEFA Europa Conference League play-off round, as well as a 1-0 defeat against Kalmar FF and a 2-2 draw against IFK Värnamo in Allsvenskan.
He debuted with a 2-1 defeat against Puskás Akadémia FC in the first round of the 2024–25 Nemzeti Bajnokság I at the Szusza Ferenc Stadion.