Carol Green, 46, was last seen in Chorley on Tuesday, October 5.
She is known to frequent Blackpool, Lytham and Southport and officers say may be in the company of a man.
Carol is 5ft 4ins and has long dark brown hair. She was last seen wearing a black jumper/cardigan and black jeans.
A Lancashire Police spokesman said: "We have so far made numerous enquiries to find her and we are now asking for the public’s help.
"We are growing increasingly concerned for Carol’s welfare and we are asking for anybody who sees her to get in contact with the police.
"Similarly, we would ask Carol to get in touch to let us know she is okay."
Anyone with information is asked to email [email protected] or call 101, quoting log 1347 of October 7, 2021.
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