Gerolf or Gerulf (c. 850 – 895/896) is the second count of this name who is attested in the area of Friesland (which also includes Holland at this time).
Gerolf's main area of power seems to have been in Kennemerland.
Count Gerolf is often regarded as the founder of the County of Holland, although the actual name "Holland" is from a later time.
His ancestry is unclear, but he may have been a son or, more likely, a grandson of the earlier Gerolf, who was a count in the area of Frisia at the time of the reign of Emperor Louis I the Pious (fl. 833) and who later joined a monastery.
The earlier Gerolf died in 855.
There is some limited and vague evidence that this earlier Gerolf was a son of a certain Theodoric, who in turn supposedly descended from the Frisian king Redbad (d. 719).
Count Gerolf is often identified as the father of Count Dirk I and seen as the founder of the first house of the Counts of Holland, which will rule the county until it was inherited by John II of Hainaut in 1299.
