Nils Mattias Joacim Asper (born 20 March 1974) is a Swedish former professional footballer who played as a goalkeeper.

A full international between 1999 and 2002, he won three caps for the Sweden men's national football team and was a squad member for them at UEFA Euro 2000.

Asper was the first choice goalkeeper for Mjällby AIF in four seasons before signing to the Allsvenskan side AIK in 1998.

On the 8 of June, Asper made his debut against Östers IF putting Lee Baxter on the bench, which would last for the rest of the season.

[1] Asper made his international debut for Sweden on 27 November 1999 in a friendly game away against South Africa, replacing Magnus Kihlstedt at halftime.