UC has ~180,000 seaweed specimens with ~50,000 from California. The collections represent voucher material for regionally and internationally important studies and include approximately 2000 type specimens. With the recent addition of 40,000 specimens from the Los Angeles County Museum (including those formerly housed at the Allan Hancock Foundation) plus many gifts from orphaned collections, our holdings of California seaweeds are extraordinary. The collections are used in systematic, ecological, and evolutionary research. They are also actively used in teaching and as resource material for identification. Seaweeds from the West Coast (i.e. NE Pacific) have been digitized and databased and are available online. The rest of the worldwide collections will be available online.