The Irvine Ranch Natural Landmarks (also known collectively as Irvine Ranch Open Space[1]) are a collection of protected areas in Orange County, California in and around Irvine.

They encompass almost 50,000 acres (20,000 ha) of land which was once a part of the Irvine Ranch owned by the Irvine Company.

[2] Irvine Ranch contains a remarkably complete stratigraphic succession ranging in age from late Cretaceous (80 million years ago) to the present.

The primary biological features at the site include coastal sage scrub and chaparral communities, including rare Tecate cypress woodlands.

By the late 1970s the cattle business had been sold.