Monaghan, 32, is starting his fifth season with the Wolves, and has scored 128 tries in 118 appearances.
Coach Tony Smith said: “Joel’s leadership qualities and knowledge of the game made him the stand-out candidate. Over the years he’s developed as a leader and has become very influential within the group. He’s highly respected by all the players and staff. I’m now looking forward to seeing him develop his leadership skills further and the positive impact it will have on the team.
“Chris’ development over recent years is quite remarkable and this again is testimony to the hard work he’s put in on and off the field. Chris leads by example and he’s not only a future Warrington captain, but I believe a future England captain. Like Joel, Chris is immensely respected by his fellow players.”
For Hill, it marks another step in his remarkable growth since arriving from Leigh ahead of the 2012 season.
Last year’s joint captain Westwood has been relieved of the role to allow him to focus on his personal game.
Smith added: “Ben still remains an influential and integral part of the team’s leadership, as do a number of other players who have missed out on the captaincy. Relieving Ben of this role will allow him to focus on getting back to his best form we all know he’s capable of.”