The Excelsior-class was a type of battleship and explorer that was first built in the 2280s and went on to be used by Starfleet throughout the 24th and 25th centuries.

The prototype of this class was the USS Excelsior (NX-2000) was initially fitted with an experimental transwarp drive and was proclaimed as "the Great Experiment".

The "great experiment" of transwarp drive was meant to revolutionize faster-than-light transport by capturing the warp envelope in a transporter field and beaming it ahead of the ship and increasing the speed in which it could travel.

Despite the ignoble start, tests continued to be ran on the Excelsior but the transwarp drive continued to prove unreliable and was declared a failure. However, the Excelsior's spaceframe proved to be very stable and reliable and it was decided to replace the transwarp engines with standard warp drive and continued with production of further starships.

Several years later, a new variant of the Excelsior-class design entered service with added modifications to the basic hull design. The first ship to be constructed to these specifications was the USS Enterprise-B which was launched in 2293.

Although some Excelsior-class vessels were built to these specifications, many new vessels used the original design.

The production run of the Excelsior-class ran well into the 24th century, which highlighted the adaptability and soundness of the basic design. However, by the early 2330s, construction on new Excelsior-class vessels was down to just two a year, as new starship classes such as the Ambassador-class came into service. Although the Excelsiors were often relegated to secondary duties by the 2360s, large numbers remained in service.

Source: Memory Beta