A major search was launched after the coastguard received a 999 call to report the missing boat at around 10.45pm on Tuesday.
It was last reported to have been near Mull of Galloway lighthouse off the coast of Dumfries and Galloway in Scotland at around 11.45am that day.
Coastguards tried to contact the yacht over VHF radio and also issued broadcasts appealing to other vessels in the area to look out for it.
A search was launched involving Portpatrick, Drummore, Newcastle, Ballycastle, Bangor and Coleraine coastguard rescue teams and the RNLI Portaferry inshore lifeboat from Northern Ireland, as well as the HM Coastguard search and rescue helicopter based at Prestwick.
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The helicopter located located the boat near South Rock, around 17 miles off Mull of Galloway, at around 10.30pm on Wednesday.
The RNLI Portaferry lifeboat went to help the yacht, which had suffered engine problems, and towed it into Portavogie, Co Down.
The person on board was safe and well and was given safety advice.