The experienced forward has secured an immediate return to the Premier League after being relegated with Watford last season
Welbeck had been without a club after seeing his contract at Watford terminated by mutual consent at the start of the month.
The 29-year-old spent one season at Vicarage Road, scoring two goals in 18 Premier League outings, and was ultimately powerless to prevent them from being relegated to the Championship.
Brighton have now handed Welbeck the chance to continue his career in the top flight, snapping him up as a free agent on Sunday.
Graham Potter believes a man who became a Premier League winner at United before spending five years at Arsenal will add high-quality depth to his attacking ranks at the Amex Stadium.
“We are delighted to have Danny joining us. He will complement our existing striking options,” the Seagulls’ boss told the club’s official website.
“He’s got an undoubted pedigree, and he is quick and technically very good. He will add to our attacking threat and we are thrilled to add another player of his experience and quality.”
Brighton technical director Dan Ashworth added: “I think Danny’s arrival concludes what we feel has been a very good window for the club.
“A lot of planning, diligence and hard work went into the recruitment side, and I would like to thank all the club’s different departments for their efforts in achieving that.”
✍️ Albion have completed the signing of striker Danny Welbeck.
The former Manchester United, Arsenal and Watford forward has agreed a one-year deal with Albion!
— Brighton & Hove Albion (@OfficialBHAFC) October 18, 2020
Welbeck could be in line to make his debut for the Seagulls when they take in a trip to Selhurst Park to face Crystal Palace on Monday.
The former England international, who has won 42 caps for his country, will now compete for a regular place in Potter’s starting line-up alongside Neal Maupay and Aaron Connolly, with the former currently among the top scorers in the Premier League.
Maupay has scored four goals in Brighton’s first four matches of the new season, but they find themselves languishing down in 16th at the moment having only picked up three points from a possible 12.