A 40-year-old woman was at the Shell garage in Caton Road when she was approached by a man on the forecourt between 11pm and 11.05pm on Thursday October 25.
The man had a knife in his hand and threatened to stab the victim unless she handed over her handbag, which included cash and bank cards.
The offender took the handbag and made off from the scene. The woman was not injured in the incident.
Following CCTV enquiries, police would like to speak to the man pictured in connection with the investigation.
Temp Det Sgt Stephen Craig, of Lancaster Police, said: “Do you recognise this man? We want to speak to him in connection with a robbery in Lancaster.
“We believe someone must know who he is. If you can help, please contact police immediately.”
Anyone with information can contact police on (01253) 596454 or email [email protected] quoting log 1556 of October 25.
Alternatively independent charity Crimestoppers can be contacted on 0800 555 111 or online at crimestoppers-uk.org