Following prolonged negotiations, TNT has renewed Rizzoli & Isles.

The cop drama starring Angie Harmon and Sasha Alexander based on the novels by Tess Gerritsen will return for a sixth season, The Hollywood Reporter has learned. The run will consist of 18 episodes — the show's largest single-season order to date.

The series, which tapped Jan Nash to take over for creator and showrunner Janet Tamaro in season five, will return in early 2015 for its three remaining episodes of the season. Nash will return as showrunner in season six, which will again return in the summer.

Thus far, season five is averaging 7.6 million total viewers when factoring in seven days of DVR viewing, ranking Rizzoli & Isles as the second-most-watched show in TNT history behind The Closer. The drama is one of basic cable's top five series every year among total viewers and was the top show on basic cable this past summer.

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The renewal delay for the series, which begins airing in syndication in fall 2015, came after TNT and TBS programming president Michael Wright exited the Turner-owned networks. Sources tell THR that Wright was in the midst of renegotiating a new licensing deal with producers Warner Horizon Television for a two-season renewal that also included salary bumps for leads Harmon and Alexander, who are said to have negotiated together.

That changed, sources said, during negotiations after former Fox topper Kevin Reilly took over for Wright. Sources said the renewal also came after USA Network expressed interest in picking up the series if a deal could not be reached with TNT. TNT denied that there was any sort of stalemate or that the show could have landed elsewhere.

Meanwhile, Reilly is said to be looking for edgier fare as Turner continues to clean house at both TNT and TBS, canceling dramas Franklin and Bash, Dallas, Perception and comedy Sullivan and Son.

Rizzoli joins a roster of new and returning dramas at TNT that includes Falling Skies, The Last Ship, Major Crimes, Legends, Murder in the First, The Librarians, Public Morals, Proof, Agent X and Transporter: The Series.

On the pilot side, TNT also has DC Comics take Titans, Jerry Bruckheimer/Michael Bay's drug trade drama, Lumen and supernatural crime entry Breed.

Rizzoli is also executive produced by Bill Haber's Ostar Productions.

Email: Lesley.Goldberg@THR.com

Twitter: @Snoodit