The Challenger Class Starship is a Federation Starship of the 2290s - 2370s.
The Challenger Class Starship is an entirely political animal. They would not exist except for a political decision inside Starfleet Command and a rebellion against that decision.
in 2285, Starfleet Command decided to withdraw the Constitution class from service and retire all existing Constitution class starships. This was against the advice of engineering and field crews who knew that the Constitution class had years more service ahead.
However, Starfleet Command was struggling with branding. The Constitution was the epitome of independent service. Constitution class captains were often isolated and acting on their own initiative. Starfleet Command wanted to rebrand itself as a centralized, competent and efficient military service, more suited to winning a war against the Klingons than exploring Strange new worlds. As a symbol of the old Starfleet, the Connies had to go.The Challenger was actually designed and built at the Denevan ship yards and described as a "Multi-Role Medium Cruiser" to supplement the highly demanded Miranda class . It was simply a combination of off-the-shelf components of the Constitution and the Constellation class . The design work was shared openly along the frontier and several less centralized ship yards began construction of the type.
There was a scandal and controversy when this was discovered by Starfleet Command, but by then it was too late.
The Challenger class starships served alongside their Miranda class, Constellation class and Constitution class sisters until the late 2360s when Borg Incursions and renewed tensions with the Klingons revealed that they were just too old to continue. The last Challenger class was withdrawn in 2371.