The Treaty of Algeron was a diplomatic peace treaty signed between the United Federation of Planets and the Romulan Star Empire.


The treaty was signed on the planet Algeron IV in 2311, two months after the Tomed Incident and approximately 160 years after the Earth-Romulan War. (TNG episode: "The Pegasus")

Representing the Federation was Ambassador Paulo Endara, a Human male. Representing the Romulan Star Empire was Ambassador Gell Kamemor, a Romulan female. Representing the Klingon Empire was Ambassador Kage, a Klingon male.

As of stardate 41986.0, Starfleet and/or the Federation had no contact with the Romulans for 53 years, 7 months, and 8 days, according to TNG episode: "The Neutral Zone". That stardate correlates to late in the year 2364, which means the last communication with the Romulan government would have been in the first half of the year 2311. This contact could be when the Treaty of Algeron is signed, or during the month after the signing to allow for diplomats, trade representatives, and other Romulan citizens to be recalled from Federation and Klingon space.

The treaty reinforced the Romulan Neutral Zone and stated the grounds that would result in the violation by either side which could be considered an act of war. One of the stipulatons of the treaty was an express prohibition of the development of cloaking technology by Starfleet. (TNG episodes: "The Defector", "The Pegasus")

The computer game Echoes From the Past states that the Treaty of Algeron created the Neutral Zone and implies this was at the end of the Earth-Romulan war. This interpretation is followed by the DC Comics Convergence story where General Tellius was involved in the Treaty two years after the end of the Earth-Romulan War.

A secret amendment was made to the treaty in 2371 which allowed limited use of cloaking devices by the Federation as long as it was supervised by a Romulan military officer. This allowed the USS Defiant to be loaned a cloaking device for its operations against the Dominion. However, the amendment stated that only a single Defiant-class vessel was allowed the use of the cloaking device and only in the Gamma Quadrant (DS9 episode & novelization: The Search)


In the year 2358, Admiral Erik Pressman attempted to circumvent the Treaty of Algeron by attempting to create an Interphase cloaking device which was secretly developed by Starfleet Intelligence which was tested on the USS Pegasus. (TNG episode: "The Pegasus")

In 2371, the USS Defiant was deployed at Deep Space 9 for operations against the Dominion and the use of the cloaking device was overseen by Subcommander T'Rul of the Romulan Star Empire. (DS9 episode & novelization: The Search)

On Stardate 72487.91, the USS Kelso was lost with all hands. It was revealed that they were testing cloaking technologies, infuriating the remnants of the Romulan Star Empire as well as the Klingon Empire. President Aennik Okeg convinced the other sides that he banned research and construction of Federation-based cloaking technologies. It was stated that the Treaty of Algeron was no longer valid with the Romulan Star Empire as it once was gone. (ST website: The Path to 2409)

However, it seems that things have changed as the Defiant-class ships and its offspring, the Galaxy X-class ships and its offspring and the brand new Avenger-class battlecruiser utilize cloaking technologies.

By 2410, the Treaty of Algeron was rendered obsolete due to the fact that the Romulan Star Empire had been dissolved due to in-fighting with Empress Sela's disappearance, leading to the once-mighty Empire being reduced to a handful of hold out colonies outside the Romulan Republic. Without the Treaty, Starfleet was able to resume usage of cloaking technology. (Star Trek Online)

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