Gertrud Billung Princess of Saxony
- Born: Abt 1028, Schweinfurt, Unterfranken, Bavaria
- Marriage (1): Floris I Holland Count of Holland about 1050
- Marriage (2): Robert I 'le Frison' of Flanders Regent of Holland in 1063
- Died: 4 Aug 1113 about age 85
Another name for Gertrud was Gertrude Billung.
Gertrude of Saxony (also known as Gertrude Billung) was the daughter of Bernard II, Duke of Saxony and Eilika of Schweinfurt. She married Floris I, Count of Holland about 1050, and upon his murder, her son Dirk V became Count of Holland. Since he was still young, she became regent.
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.
In 1063 Gertrude married Robert of Flanders (Robert the Frisian), the second son of Baldwin V of Flanders. This act gave Dirk the Imperial Flanders as an appanage - including the islands of Frisia west of the Frisian Scheldt. She and her husband then acted as co-regents for the young count.
Gertrud married Floris I Holland Count of Holland, son of Dirk III Count Of Holland & West Friesland and Otelhild Princess Of Saxony, about 1050. (Floris I Holland Count of Holland was born about 1017 in Vlaardingen, Zuid-Holland, Netherlands and died on 28 Jun 1061 in Nederhemert, Gelderland, Netherlands.)
Gertrud next married Robert I 'le Frison' of Flanders Regent of Holland, son of Baldwin V Count Of Flanders and Adèle (Alix) Capet Princess of France, in 1063. (Robert I 'le Frison' of Flanders Regent of Holland was born in 1033 in Flanders, Belgium and died on 13 Oct 1093 in Kassel, Hesse, Germany.)