Arsenal confirmed the news on the club website. Terms of the deal were not disclosed.
Ramsey spoke about the deal in the release:
I'm delighted to have signed a new contract. I've been here for six years and I'm so happy. I think we've shown so far this season what we're all about and the direction that this club wants to go in. I want to be a part of that, and to be a part of something special at Arsenal. We have a great team which we believe can achieve great things.
Ramsey signed with the club at the same time as Santi Cazorla and youngster Gideon Zelalem, and manager Arsene Wenger spoke about extending the trio:
We are very pleased that Santi Cazorla, Aaron Ramsey and Gedion Zelalem have committed their futures to the Club. Cazorla and Ramsey are absolutely key players for us, and this news is a boost to the whole club. Gedion is very young of course, but he has shown already that he has fantastic promise, and we all look forward to his development with us.
Ramsey displayed great potential during the early stages of his career. He finally put all of that talent together to shine for Arsenal throughout the current campaign. He's been a force in the midfield, creating quite a trio with Mesut Ozil and Santi Cazorla.
In turn, Arsenal decided to reward him with an extension that rewards him from that terrific form and should ensure he remains at the Emirates for the foreseeable future.
The 23-year-old Welsh international has been the club's best player this season with a 7.79 overall rating, according to WhoScored.com. The only thing that's held him back is a thigh injury, which has kept him on the sidelines since late December.
Although Arsenal remain in the championship chase heading into the stretch run, his absence has certainly played a role in their inability to main the top spot. He was the driving force behind the Gunners' attack for the early portion of the season.
By locking him up with a contract extension now, Arsenal are hoping he can build off that success and continue to perform like an elite midfielder. Putting the injury woes behind him is obviously a major part of that process for the remain portion of the current campaign and beyond.
It's a high price to pay for a midfielder who's just starting to come into his own. If he struggles to replicate that success in the future, it could turn into a costly mistake by the Gunners. But Wenger and Co. are clearly confident that won't be the case.
Looking ahead, Ramsey has enough talent to assert himself as one of the best midfielders in the Premier League for the duration of the contract. He's a creative distributor, showed off his finished ability this season and can also track back to help defensively.
And while it's impossible to know if he's going to live up to his new contract, Arsenal decided he had shown enough to sign him now rather than wait and risk losing him.
If all goes according to plan he'll be a major piece of the puzzle with Arsenal for many years to come.