FK Radnik Surdulica (Fudbalski klub Radnik Surdulica) is a professional Serbian football club based in Surdulica. The club traces its origins to 1926, when it was established as Surdulički sportski klub (SSK) through the initiative of local craftsman Gradimir Antić. The club later went through several name changes before adopting the name FK Radnik in 1950. Radnik spent much of its early history competing in lower levels of Serbian/Yugoslav football before achieving significant progress in the 2010s. In the 2014–15 season, Radnik won the Serbian First League and earned promotion to the Serbian SuperLiga for the first time in its history. The club plays its home matches at Gradski stadion in Surdulica, which has a reported seating capacity of 3,312. Its official address is Vase Smajevića bb, Surdulica. Radnik has also maintained a focus on youth football and the development of young players from the surrounding region. The club currently competes in the Serbian SuperLiga; the official league page lists Radnik in the 2026/27 competition. Over its history, the club has established itself as an important football institution in southern Serbia, representing Surdulica in Serbia's national football system.