The Brazilian has made 208 appearances for the Reds since joining from Gremio in July 2007.
Lucas has had his injury problems over the past couple of seasons and was out from mid-August until December with a thigh problem.
It is less than two years since the 26-year-old last signed an improved contract but the midfielder took little persuading to agree a new deal.
"It's another long-term contract that I have signed, but it was the same feeling as when I first came here," he told liverpoolfc.com.
"I am really delighted to have the opportunity to play for this club.
"It's where I think I belong and where I wanted to stay, so I am very happy and looking forward to a few more years here.
"It was an easy decision because after the long period of my career I have had here I would like to give the best of my time to this club.
"It was not a difficult decision to make and I am really looking forward to what will hopefully be a few more years with a lot of success."
Managing director Ian Ayre said the new contract was just reward for the Brazilian's commitment, as well as being important for manager Brendan Rodgers' long-term planning.
"It's fantastic. He has been such a great servant to the club and I think during the period he went through with his two injuries, he put so much work into it and the club supported him through it," he said.
"He just goes from strength to strength. We said throughout last summer and January, we wanted to keep our best, experienced players, and this is another great example of that.
"The manager has said several times that as well as having a great, young squad, it's important we have experience and it's important we have characters. People like Lucas fit that.
"He'll tell you he's still very young but in footballing terms he's experienced and a big part of the team."
In the last 10 months Luis Suarez, Daniel Agger, Martin Skrtel, Brad Jones, Raheem Sterling, Suso, Jonjo Shelvey, Martin Kelly and Andre Wisdom have all signed new deals with another in the pipeline for captain Steven Gerrard.