Großseifen (or Grossseifen) is an Ortsgemeinde – a community belonging to a Verbandsgemeinde – in the Westerwaldkreis in Rhineland-Palatinate, Germany.

The river Nister, which is in the Sieg drainage basin, flows east to west through the community.

Großseifen belongs to the Verbandsgemeinde of Bad Marienberg, a kind of collective municipality.

This community near Bad Marienberg had its first documentary mention on 6 January 1307 when Count Heinrich of Nassau with his wife Adelheid confirmed to the abbot and convent of the Marienstatt Cistercian Monastery the existing revenue in Velde (=Fehl/Fehl-Ritzhausen) and Graynsiven.

The name's ending of –siven, –sifen or –seifen describes a kind of wetland found in the area.