The elderly woman was shopping in Asda in Llanelli when Neil Staton stole her handbag.
Staton, of Port Tennant in Swansea, was jailed for 24 weeks.
He was arrested, charged and sentenced within 24 hours of the incident taking place.
The 62-year-old singled out the elderly woman as his victim at around 1pm on June 13 and was seen loitering around her while she did her shopping.
He reached into her trolley and stole her handbag, which contained more than £100, before hiding it in a carrier bag and leaving the store.
He used her money to place bets in a shop nearby.
The crime was reported to police immediately, and CCTV footage was quickly obtained by officers, clearly showing Staton as the offender.
He was located by officers driving along Station Road, who recognised him from the CCTV images.
Staton was swiftly arrested, and indicated where he had abandoned the bag during police interview. Officers found the bag in a wheelie bin behind Station Road, still containing the victim’s personal items.
They were able to return it to the owner the same day, and Staton was charged with theft.
He appeared at Llanelli Magistrates’ Court the following day, where he admitted the offence and was jailed for 24 weeks. He was also ordered to pay £100 in compensation to the victim.
Sergeant Ben Ashton said: “The suspect preyed on a vulnerable woman for his own gain, and we are pleased with the prompt outcome.
“Staton was identified, located and arrested swiftly, and we were able to return the victim’s handbag which contained items of sentimental value within hours of it being stolen, for which she was very grateful.”