Jakob Ahlmann Nielsen (born 18 January 1991) is a retired Danish professional footballer who played as a left-back and current scout at AaB.

In 2006, two years after his transfer to AaB, however, he moved to FC Midtjylland, to play for their youth academy.

At the beginning of the 2011–12 season, Ahlmann was again included in the first team, where Patrick Kristensen had played in the same position.

Lucho had also been brought to the club in the summer transfer window, who could also play left back.

[7] At the end of the 2011–12 season, Jakob and his brother Viktor Ahlmann both signed contract extension with AaB.

He also played the entire match of the 2013–14 Danish Cup final, which ended in a 4–2 win over FC Copenhagen in Parken Stadium on 15 May 2014.

[20] In May 2024, AaB announced that Ahlmann would be retiring from football at the end of his contract, continuing on at the club as a scout.

The day after AaB won the Superliga, on 12 May 2014, Ahlmann was called up for the Denmark senior team for the first time by national coach Morten Olsen for the matches against Hungary and Sweden, along with fellow AaB players Kasper Kusk, Rasmus Würtz and Nicolaj Thomsen.

[25] His debut match ended 2–2, on Danish goals scored by Christian Eriksen and Lasse Schöne.

[26] After failing to make an appearance for the national team for six years, Ahlmann returned in action in November 2020, where he came on as a late substitute in a friendly against Sweden.