Santa Rosae was an ancient landmass off the coast of present-day southern California, near Ventura County and Santa Barbara County, of which the Channel Islands of California are remnants.

Before the end of the last ice age, the northern four Channel Islands of California were linked in a single contiguous island only 4.7 miles offshore. Geography took its present shape after the continental ice sheets melted and sea levels rose 120 metres. There is also evidence to suggest that a submerged island, Calafia, lay between Santa Rosae and the mainland.

Santa Rosae is perhaps best known for its population of pygmy mammoths (Mammuthus exilis) that went extinct some 10,000 years ago in addition to the fact that it was home to the Arlington Springs Woman.