His decision was first reported by The Dallas Morning News and Fort Worth Star-Telegram.
Asked about other potential gubernatorial candidates, he said: "I don't know about them, but it will be Perry in 2010."
Perry will become the longest-serving governor in Texas history later this year. He took over for George W. Bush after Bush was elected president in 2000 and has won two four-year terms since.
Asked what he hoped to accomplish with a third term, Perry said transportation infrastructure, economic development and public education improvements are works in progress "and we still want to continue moving Texas forward."
Perry insiders seemed to expect the announcement.
"This is not surprising; it's been a possibility all along, since he got re-elected," said Republican consultant and former Perry speechwriter Eric Bearse.
Perry spokesman, Robert Black, was not as definitive.
"I think it would be safe to assume that Rick Perry is a candidate for governor in 2010 unless he says otherwise," said Black.
But, Black said much would be determined after the next legislative session convenes in January. A possible third term would give Perry more leverage to accomplish his legislative priorities, which are expected to include tax rebates and spending transparency.
There are no term limits for Texas governors, but governors have historically only run for two terms since terms were set at four years.
Most recently, Perry bested a Democrat and two independent candidates in 2006, garnering 39 percent of the Texas vote in what was a wacky and unpredictable campaign even by Texas standards.
Republican Sen. Kay Bailey Hutchison also has said she is considering a run for governor in 2010. But she backed away from an aide's statement last month that she was indeed planning a run for the state's top political post.
She's twice considered taking on Perry, most recently in 2006, but decided against what would then be a divisive primary battle.
Hutchison said earlier this month that if she runs in 2010, "there's not anyone who could really make a case to me that this would be divisive for the Republican Party in a way that would make me step back."
She said Thursday that it was still "too early to make an announcement about the 2010 race" and questioned the certainty of Perry's comments.
"I think that it's not the time for us to be focusing on 2010," she said. "Maybe he didn't say something definitive ... I'm not saying he was announcing _ I doubt that he was, but I do think talk of 2010 is not good in April of 2008."
Republican Lt. Gov. David Dewhurst, who also is considered to be eying the position in 2010, said Thursday that he's focusing on the upcoming legislative session.
For now, Perry's announcement puts to rest speculation that he has been angling for a vice presidential nod, spurred on by his increasingly frequent national appearances including endorsements of failed presidential hopeful Rudy Giuliani and more recently likely Republican presidential nominee Sen. John McCain.
"Being the governor of the state Texas is a great job," Perry said Thursday. "I do not have an interest in going to Washington, D.C., and being somebody's vice president."
Perry said he could do more for Texas by being in Texas "and that's where I'm going to spend my time over the next three to seven years, making a difference in Texas."
Perry angered many conservative Republicans in the state with his endorsement of the former New York City mayor, who has far more liberal stances on issues like abortion, gay rights and guns.
But, Perry seemed to return to the conservative fold when he published a book about the Boy Scouts that attacked the American Civil Liberties Union in what he characterized as a moral struggle for the country's future. Perry has made numerous appearances around the country, including one Thursday in Fort Worth, to promote "On My Honor: Why the American Values of the Boy Scouts Are Worth Fighting For."
Perry started his political career as a Democratic member of the Texas House from his rural hometown, Paint Creek in 1982. He rose through the ranks as agricultural commissioner, lieutenant governor and then governor.
Speculation about Perry's future seemed to intensify in recent weeks, as bumper stickers with the "R'' insignia that Perry has used in campaign materials and the slogan "Again in 10" popping up around Austin.
"It's hard to walk away from that," said Austin Republican consultant Bill Miller. "It's a way of life."