Mathias Alexander Nilsson (born 23 February 1999) is a Swedish professional football player who plays as a goalkeeper for Superettan side Trelleborg.
On 15 February 2024, Nilsson moved to Finland after signing a loan deal with a newly promoted Veikkausliiga club IF Gnistan for the 2024 season. On 8 August 2024, his loan deal with Gnistan was terminated and he joined Gefle in Superettan.