Adelaide was born as the daughter of Otto I, Count of Guelders and Ricardis of Bavaria. We knew next to nothing about her youth, and we don’t know the year she was born. She first appeared in contemporary records when she married William I, Count of Holland. William was the younger brother of Dirk VII, Count of Holland.
William was attacked with the permission of his brother but managed to escape, and he fled the court of Guelders. He apparently remained there a while because he suffered from frostbite and while there he became engaged to Adelaide. The wedding was celebrated in Stavoren, around 1198. William was probably around 30 years old but Adelaide could have been as young as 10 years old or as old as 20 years old. Her skeleton was found and it was estimated that she was around 40 years old when she died in 1218.
Until 1203, William only ruled the area of Friesland, and upon his brother’s death, he tried to overthrow his niece Ada and her husband, Louis. He managed to finally do this in 1206, making him Count of Holland and Adelaide his Countess. Adelaide and William went on to have five children together: Floris (later Count of Holland), Otto (later Bishop of Utrecht), William (later regent of Holland), Ricardis (remained unmarried and founded the Koningsveld Abbey)and Ada (later Abbes at Rijnsburg)
Adelaide was known to have had her own seal, but it has not survived. In the spring of 1217, William left to join the Fifth Crusade, and Adelaide died in his absence on 12 February 1218. She was interred in Rijnsburg Abbey. Her husband did not return home until May 1220. He gave money for masses to be said for the souls of his ancestors, his wife and for him.