Gertrude of Saxony (c. 1030 – August 4, 1113), also known as Gertrude Billung, was a countess of Holland by marriage to Floris I, Count of Holland, and countess of Flanders by marriage to Robert I, Count of Flanders.

When Dirk V came into power, William I, Bishop of Utrecht, took advantage of the situation, occupying territory that he had claimed in Holland.

Gertrude and her son withdrew to the islands of Frisia (Zeeland), leaving William to occupy the disputed lands.

This act gave Dirk the Imperial Flanders as an appanage – including the islands of Frisia west of the Frisian Scheldt.

When her spouse left for a journey to Jerusalem in 1086–1093, Gertrude served as regent of Flanders during his absence.