The 38-year-old joins the Tigers having spent 20 years at St James' Park.
Hull becomes Harper's second permanent club in two decades. The Seaham native joined Newcastle in 1993 but spent time his first five years with the Magpies on separate loan spells with Bradford, Gateshead, Stockport and Hartlepool.
He began to threaten first-team regular Shay Given at the turn of the century, playing in Newcastle's FA Cup final defeat to Manchester United in 1999 and notably keeping a clean sheet against Juventus in a Champions League group game in 2002.
After finally becoming the undisputed number one choice on Tyneside during Newcastle's season in the Championship, Harper signed a new contract in 2009 but two years later he found himself at Brighton on loan.
He played his last game for Newcastle - acting as captain - in a 1-0 Premier League defeat to Arsenal in May and despite reports suggesting he was ready to retire, he attracted the interest of Hull, who have now handed the veteran another stab at top-flight football.
A statement published by Hull's official Twitter feed, @hullcityteam, read: "We are delighted to announce the signing of Steve Harper on a one-year deal £WelcometoHull £hcafc"
Steve Harper: "I came down this morning and had a very thorough medical, and then trained with them all this afternoon.
"I was told they're a good bunch of lads and paths have crossed with the gaffer a few times as well.
"It was great to see them play and 3-5-2, you don't see that very often, but it worked and they passed the ball well.
"I'm looking forward to it. It's a new challenge, a new chapter. It won't be as long as the last chapter, but I'm looking forward to it.
"I've said to Allan and Eldin, the other goalies, I'm here and we're all in this together.
"It's going to be a long year in this league, but we're going to have a right good go.
"I've probably been there and seen it in this league, and certainly after 20 years at Newcastle, you've seen quite a lot as well.
"I'm here to be competitive and make it hard for the manager, and give him a selection dilemma when it comes to the goalkeeping department."
Source: Newcastle United Mad