Matěj Šín (born 2 June 2004) is a Czech professional footballer who plays as a midfielder for Eredivisie club AZ and the Czech Republic national team. Club career Šín started his career at local side Polanka, and spent a season with Vítkovice before joining Baník Ostrava in 2014. In June 2022, shortly after his eighteenth birthday, Šín was diagnosed with testicular cancer, and immediately underwent surgery. He had featured for the first team and reserves of Baník Ostrava at the time, having made his debut at the age of seventeen, but had to put his career on hold as he underwent post-operative treatment, and was unable to partake in any strenuous activity, such as football. In October 2022, it was announced that Šín had overcome the cancer and begun training individually, hoping to return to his former club Baník Ostrava. The same month, he sent a message of support to compatriot Matěj Pinkas, an ice hockey player of the same age who was also suffering from cancer at the time. Šín returned to first team training with Baník Ostrava in January 2023. The following month, he scored his first goal for the club, though it was a consolation goal in a 2–1 away loss against Zbrojovka Brno. Just over a week later, he signed a professional contract with the club, keeping him with Baník Ostrava until June 2025. On 29 August 2025, Šín signed a five-year contract with Eredivisie club AZ. International career Šín has represented the Czech Republic at youth levels ranging from under-16 until under-20. On 23 March 2025, he debuted for the Czech senior squad in a 2026 FIFA World Cup qualification against Faroe Islands, ending in a 2–1 victory for the Czechs.