Gertrude of Saxony, 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. She was regent of Holland in 1061-1067 during the minority of her son Dirk V, and regent of Flanders during the absence of her spouse in 1086-1093.