Mariann Gajhede Knudsen (born 16 November 1984) is a retired Danish footballer who last played as a central midfielder for Linköpings FC of Sweden's Damallsvenskan.

She won over 100 caps for the Danish national team, before announcing her retirement from international football in November 2014 and making a brief comeback the following year.

Gajhede Knudsen represented Fortuna Hjørring in both legs of the 2003 UEFA Women's Cup Final, a 1–7 aggregate defeat by Umeå IK of Sweden.

[6] In Denmark's opening group match against hosts Sweden Gajhede Knudsen gave her team the lead in an eventful 1–1 draw.

[7] In November 2014, exhaustion and niggling injuries caused Gajhede Knudsen to reluctantly withdraw from national team selection, allowing her to focus on club football.