One of the most notable Ambassador-class ships was the USS Enterprise-C. In 2344, while under the command of Captain Rachel Garrett, the ship responded to a distress call from a Klingon colony on Narendra III. Four Romulan warbirds had surrounded the colony. The Enterprise responded to the attack, and despite being destroyed there, defended it long enough to impress the Klingon High Council; hostilities ended almost immediately between the Klingon Empire and the Federation. (TNG: "Yesterday's Enterprise")
Ships of the Ambassador-class were utilized in the 24th century during the Klingon Civil War, and fought against the Borg and the Dominion. (TNG: "Redemption II"; DS9: "Emissary", "You Are Cordially Invited")
The Ambassador-class featured the saucer section-engineering section-warp nacelle layout common to most Starfleet vessels. It was intermediate in size between the Excelsior-class and the Galaxy-class. In addition, the class boasted at least three engineering levels. (TNG: "Yesterday's Enterprise")
A number of Ambassador-class ships were constructed with minor alterations from the original design. The saucer section's connection to the engineering hull was shifted slightly aft, with the nacelle pylon assembly moved a corresponding distance in the same direction. Cowlings were added around the Bussard collectors, making them appear closer to that of the Galaxy-class, while the impulse engine exhaust changed from a blue to a red glow. The lower sensor dome became more elaborate and closer in appearance to the Excelsior-class and the deflector dish was modified. Finally, the width of the shuttlebay was increased and a second facility resembling that on the Excelsior-class engineering hull was mounted directly underneath the original one. Graphics were upgraded with the Starfleet insignia of the 2360s. (TNG: "Data's Day"; DS9: "Emissary")
According to Natasha Yar, during the 2340s, the Ambassador-class had "a lot more maneuverability than the Romulan counterparts of that era." Yar went on to explain that in her alternate timeline, deflector shield technology of the 2360s would advance considerably during the war, allowing the Galaxy-class to posses a heat-dissipation rate that was almost double those of the Ambassador-class, allowing the Galaxy to hang in a firefight longer. (TNG: "Yesterday's Enterprise")
Primary operational control of the Ambassador-class starship was provided by the main bridge. Located on top of the primary hull, the bridge directly supervised all primary mission operations and coordinated all departmental activities.
In 2344, the central area of the bridge provided seating for the captain only. Directly fore and to the right of the captain was the ops station, with the helm station to the left. The consoles were similar to that used on the bridges of Excelsior- and Galaxy-class starships. At the very front of the bridge was a large viewscreen, with a freestanding console located directly below. Against the back walls of the bridge were consoles for the tactical, engineering, and science positions. Additional displays flanked the aft consoles. The bridge was accessed through two doors, located on the forward halves of the port and starboard walls. (TNG: "Yesterday's Enterprise")
The original design incorporated flat-panel, LCARS-based, control panels using the interface introduced in the late 23rd century. (TNG: "Yesterday's Enterprise") By the 2360s, the Ambassador-class bridge was upgraded to include the standard LCARS interface and consoles typically found on board modern vessels of that era. (TNG: "Redemption II")
- USS Enterprise (NCC-1701-C)
- USS Excalibur (NCC-26517)
- USS Horatio
- USS Yamaguchi (NCC-26510)
- USS Zhukov (NCC-26136)
Very little is known about the Ambassador-class starship, whose designation dates back to an early draft of TOS: "Patterns of Force", which describes the source of cultural contamination arriving aboard a small Ambassador-class vessel called the Magellan. The term was later used in TNG: "Conspiracy" to describe the starship Horatio. It was connected to the Enterprise-C design on display graphics in "Yesterday's Enterprise."
Michael Okuda did designate a class ship in Star Trek: The Next Generation Writers' Technical Manual, 3rd ed., page 28:
- USS Ambassador (NCC-10521)
The first and subsequent editions of the Star Trek Encyclopedia popularized a length of 526 meters for Rick Sternbach's final design. Several years before the Encyclopedia was published, the number had been added to the internal document Star Trek: The Next Generation Writers' Technical Manual, which also gives an imperial equivalent of 1725 feet. No reasoning has been provided for this size.
Gary Kerr calculated a second figure of 1,570 feet and a metric conversion of 478.5 meters, explaining that the Enterprise-C is just short of 35.75 inches long in the blueprints of its miniature, and that the blueprints are in scale with the four-foot miniature of the Enterprise-D.  Kerr used 2,108 feet for the length of the latter and 48 inches for the length of the four-foot miniature, although he also determined that it was probably closer to 49.25 inches long.  Nevertheless, Rick Sternbach fully supports the 1,570-foot calculation, saying that he worked with the same assumptions when drafting the Enterprise-C blueprints. 
Aside from the unexplained figure of 526 meters, it is unclear whether the size implied by Rick Sternbach was deliberately changed during the original development process. His initial full-scale blueprints were blown up by 15%, which means that the final size of the miniature (41.19 inches) could have influenced the ship's conceptual size next to the Enterprise-D.  Greg Jein does not recall scaling up the blueprints, and whoever did remains unknown. 
Andrew Probert has stated that his original concept is exactly 1,720 feet long (524.256 meters). The number is consistent with an early TNG size comparison chart, also provided by Probert, although he did not write the 1,721-foot callout on that drawing.  
- see main article: Ambassador class model
According to the Star Trek Encyclopedia and the Star Trek: The Next Generation Technical Manual, the prototype of this class was the USS Ambassador, registry number NX-10521. (USS Ambassador at Memory Beta, the wiki for licensed Star Trek works)
The Star Trek: The Next Generation Technical Manual further established that the Galaxy-class was designed to replace the aging Ambassador- and Oberth-classes as primary instruments of Starfleet's exploration programs. (pg. 1) The Technical Manual also explained that during the design phase, the combined vehicle mass of Ambassador was expected to be at least 3.71 million tons. (pg. 75)
A line in the final draft script of "Yesterday's Enterprise"  establishes that the initial crew complement of the Enterprise-C was seven hundred. The line was not included in the final cut of the aired episode.
Ships of the Line 2012
- Category: Explorer/Emissary
- Length: 524.256 meters
- Width: 283.006 meters
- Height: 101.955 meters
- Mass: 3,710,000 metric tonnes
- Number of Decks: 33
- Officer crew: 320
- Enlisted crew: 1,000
- The DS9 novel Antimatter mentions the Ambassador-class USS Hannibal under construction at the newly-reopened Okana shipyards on Bajor's surface.
- The Ambassador-class Excalibur was the star of the Peter David Star Trek: New Frontier novel series.
- The USS Gandhi, listed here as an Ambassador-class ship, is stated as being a Galaxy-class ship in John Vornholt's Double Helix book, Quarantine.
- In the Star Trek: Typhon Pact novel Rough Beasts of Empire, the USS Assurance is an Ambassador-class starship in service at the time Starfleet's war with the Tzenkethi.
- In non-Trek related media, a cartoon version of the Ambassador-class vessel appeared in an episode of the Cinar-Paramount animated series The Busy World of Richard Scarry. A Futurama parody of an Ambassador-class, with Scott Bakula at the helm, also appeared in the direct-to-DVD film Bender's Game.
- The Ambassador-class ships Excalibur and Zhukov make appearances in the Star Trek: Bridge Commander PC game.
- In Star Trek: Elite Force II, an Ambassador-class was among the ships sent to intercept Sphere 634, due to the game's reuse of Bridge Commander ship models.
- The Ambassador-class was released as a playable starship as part of the third anniversary for the game Star Trek Online. In the game, the player gets the opportunity to take command of the USS Enterprise-C after she winds up in the 25th century instead of returning to Narendra III at the end of Yesterday's Enterprise.