The actress Honeysuckle Weeks, who starred in the ITV drama Foyle's War, is missing.
Sussex Police said officers had been searching for the 36 year old from Petworth in West Sussex, since 22:00 BST on Thursday.
The force said they were concerned for her welfare, as she had told family and friends she was feeling anxious and it was unlike her not to be in touch.
She was last seen an hour earlier in Chichester.
Det Kate Wilt said: "If you read this Honeysuckle, please get in touch to let us know you are ok."