The England international had been linked with a move away from Villa Park, but has now committed his future to the club he joined from Leeds United in 2009.
Speculation surrounding a potential exit had intensified when Delph was omitted from the matchday squad for Saturday's FA Cup clash against Bournemouth.
However, Villa announced his new contract 10 minutes before the fourth round fixture kicked off.
"The club has given me a great platform to perform and a great opportunity to showcase what I can do," Delph told Villa's official website.
"The fans have been great with me, the chairman has been absolutely fantastic with me and I have a great relationship with the manager and I see the boys here as my brothers, my family and I am delighted to stay here.
"I am a loyal person and committing my future will hopefully show everybody what type of guy I am.
"There was no way I was going to bail out. I am here for the long run."
Delph has become a key figure in the Villa squad and was named as the fans' and players' player of the season for 2013-14.
Manager Paul Lambert added: "It's great for Aston Villa. It's great for Fabian. I think this is a massive, massive step.
"The thing with modern-day football and loyalty is there's not so much of it - you very rarely get people who stay at a football club for a long, long time.
"No-one expected it. I think everyone thought Fabian was going to go and we would have to get someone else in. I don't think anyone saw this coming.
"But it's been something we've been trying to do, as I have always said.
"He enjoys his football and being at the club."
