Mads Fenger Nielsen (born 10 September 1990) is a Danish professional footballer who plays as a centre-back for AC Horsens.

[2] Having previously spent his entire senior career at Randers FC, Fenger holds the record for most first team appearances in the history of said club.

Mads Fenger grew up in Aarhus, Jutland and started his football career at local club IK Skovbakken.

[11] He quickly established himself as an important member in manager Jakob Michelsen's side, usually pairing up with compatriot Bjørn Paulsen in the central defence.

[12] After making ten appearances for Hammarby, Fenger was ruled out for the remainder of the season following a serious groin injury, which he attracted in a 2–1 win against IFK Göteborg on 20 September.

[17] In 2020, a season postponed due to the COVID-19 pandemic, Fenger continued as a regular starter and played 28 league games, although the side disappointedly finished 8th in the Allsvenskan table.

[18][19] On 30 May 2021, Fenger won the 2020–21 Svenska Cupen, the main domestic cup, with Hammarby through a 5–4 win on penalties (0–0 after full-time) against BK Häcken in the final, where he scored his attempt.

[2] Fenger featured in the final of the 2021–22 Svenska Cupen, in which Hammarby lost by 4–5 on penalties to Malmö FF after the game ended in a 0–0 draw.