Phacelia argillacea is a rare species of flowering plant in the borage family known by the common names clay phacelia and Atwood's phacelia. It is endemic to Utah in the United States, where it is known only from one canyon in Utah County. It is "one of Utah's most endangered species"; it is "one of the nation's rarest plants" and is federally listed as an endangered species of the United States.
Phacelia is only found in one county in the entire United States, and is protected because of it.