The 24-year-old - who joined Chelsea from Portuguese side Benfica after the 2010 World Cup finals for a reported 22million euros ($29million) - made his 50th appearance for the club in Saturday's 1-0 defeat by West Brom which signalled the end of manager Andre Villas-Boas.
"I am very happy with my new contract," Ramires told the club's official website.
"I am very happy with the support I have playing for this club so I want to say thank you to Chelsea."
Chelsea's loss to West Brom leaves them three points adrift of the last Champions League spot held by Arsenal while they also face two crucial cup clashes.
They face Championship side Birmingham City away in a FA Cup fifth round replay on Tuesday and then next week try to overhaul a 3-1 deficit at home to Italian side Napoli in the Champions League Last 16 second leg match.
Source: AFP
Source: AFP