Treaty of Sirius:
An agreement signed by the Kzinti and Earth following the end of the Earth-Kzin Wars. The treaty ordered the complete demilitarization of the Kzin, and only a small police force was allowed to operate. Another clause was that Earth, and later the United Federation of Planets, were allowed unrestricted access into Kzinti territory.
Treaty of Cheron (2160):
The Treaty of Cheron brought an end to the Romulan Wars in 2160 and established the Romulan Neutral Zone. Originally signed by the Romulans and the United Earth government, the treaty was renewed when the Federation was brought into existence the next year. The Treaty of Algernon renewed the status of the Neutral Zone. This treaty was also negotiated entirely over subspace radio.
Rigel Accords (2184):
The Rigel Accords brought the planet Rigel V into the Federation in the year 2184.
Interstellar Comprehensive Trade Act (2197):
A trade agreement signed between Vulcan and Earth. The famous Ambassador Sarek took part due to his familiarity with humans.
Seldonis IV Convention (2248):
The Seldonis IV Convention outlines the treatment of prisoners of war. Signatories to the Convention are prohibited from torturing prisoners and are required that they be provided with adequate food, shelter, medical attention, and other such basic necessities. Most major powers in the galaxy have signed it, such as the Federation, the Cardassians, the Klingons, and the Romulans.
Treaty of Armens (2255):
The Treaty of Armens was signed in 2255 by the Sheliak Corporate and the Federation. A number of Class H worlds were ceded to the Sheliaks as per this treaty, which contained 500,000 words and which took 372 Federation legal experts to draft. It was accidentally violated in 2276 by colonists on Tau Cygna V, a planet ceded to the Sheliak by the treaty. The colony was eventually removed in 2366. It also provided for the creation of a buffer zone between the two powers.
Treaty of Cestus III (2267):
After the destruction of a Federation outpost on Cestus III by the Gorn, this treaty was signed clearing up any misunderstandings as to borders and sovereignty thus allowing the Federation to establish a colony on the planet.
Organian Peace Treaty (2267):
This treaty was imposed on the Klingons and the Federation in 2267 after the Federation attempted to stop the Klingons from occupying Organia, a world located strategically near oth governments' borders. The non-corporeal Organians wouldn't allow for it so they declared that the planet would go to those who could develop and manage it most successfully and that each side was to open their own facilities, such as space stations, to crews from the other side.
Neutral Zone Treaty (2267):
Established in 2267 between the Klingon Empire, Romulan Star Empire and the United Federation of Planets, this treaty resulted in the creation of an experimental joint colony on Nimbus III, located within the Romulan Neutral Zone, to be managed by all three powers in an experiment in cooperation.
Polaric Test Ban Treaty (2268):
This treaty prohibits the use of polaric ion energy sources. Such energy can power an entire planet, but its use also entails a high risk of serious and uncontrolled subspace chain reactions. After the near destruction of the Romulan research colony on Chaltok IV from such a reaction, the Romulans, Federation, and other powers signed the Polaric Test Ban Treaty.
Treaty of Ectair (2274):
The Treaty of Ectair was an agreement signed by the United Federation of Planets and the Romulan Star Empire in 2274 as a result of an encounter at the planet Ectair a year earlier. This treaty allowed the Romulans access to non-Federation worlds along the frontier provided they did not cross the Romulan Neutral Zone or approach within five light-years of any Federation planet.
Genesis Nonproliferation Treaty (2285):
Prohibits the signatories, including the Federation, from using the Genesis device as a weapon of war.
Khitomer Accords (2293):
The destruction of the Klingon moon Praxis brought about environmental damage to Qo'noS and crippled the Empire's energy production, breaking the back of the Klingon war machine. To avoid the coming economic ruin, Klingon Chancellor Gorkon made the pragmatic choice of peace with the Federation. Though he was assassinated before being able to sign, his daughter Azetbur was able to represent the Empire. These Accords allowed for the Federation and the Klingons to normalize relations and eliminated the Klingon Neutral Zone.
In 2372, Gowron withdrew the Klingon Empire from the Khitomer Accords in response to the Federation Council's condemnation of his invasion of the Cardassian Union.
In 2373 Gowron reinstated the treaty when an alliance between the Dominion and the Cardassian Union threatened to throw the Alpha Quadrant into war.
The treaty was later amended banning the use of subspace weapons.
Treaty of Algernon (2311):
This treaty has shaped the course of relations between the Federation and the Romulan Star Empire, and is well known for prohibiting Starfleet's use of the cloaking device. Following the Tomed Incident in 2311, the Treaty of Algernon provided for the continuation of the Neutral Zone and provided that any incursion into that region of space without adequate warning to the other side would be considered an act of war. It also prohibits the Federation from using cloaking devices on Starfleet vessels or developing the technology at all. This section of the treaty was amended in 2371 and allowed for the limited, supervised, use of at least one cloaking device on loan from the Romulans. Operation of the cloaking device was to be limited to the Gamma Quadrant. In return, the Romulans would receive all information the Federation obtained on the USS Defiant's voyages into the Gamma Quadrant, most importantly any information concerning the Dominion. As such, the Defiant was the only Federation ship to be permanently equipped with a cloaking device before and during the war. After the Dominion War in 2375 this section was further modified allowing for limited use by Starfleet.
Treaty of Alliance (2346):
The Treaty of Alliance was signed in 2346 and brought an end to mutual hostilities between the Federation and the Klingon Empire. This treaty also provided for the groundwork for mutual military deployments and diplomatic exchanges. Under the terms of the treaty, either power may provide aid and defense to the other, but interference in domestic affairs is strictly prohibited.
Tholian Accords (2360):
Signed in 2360, the Tholian Accords established diplomatic relations between the Federatin and the Tholian Assembly, a traditionally hostile power. It also established the borders of Tholian space, closing those same borders to ships of both sides, and established protocols for diplomatic communications between the Federation and the Tholians.
Klaestron-Federation Extradition Treaty (2369):
A treaty that regulated extradition of Federation citizens who had committed crimes on Klaestron IV to the Klaestron government. Apparently it was only applicable to people residing in Federation space.
Federation-Cardassian Treaty (2370):
The Federation-Cardassian Treaty was signed in 2370 after talks were opened in 2367. The treaty withdrew the boundaries between the two powers, and created the Demilitarized Zone as a buffer. Due to this treaty, some Federation colonies found themselves under Cardassian rule, and some Cardassian colonies were under Federation control. Tension followed as the Maquis were formed. The treaty prohibits military activity, including outposts and fleet exercises, within the Demilitarized Zone. It was not popular when it was drafted, and it was nullified when the Dominion occupied Cardassian space.
Treaty of Bajor (2375):
The Treaty of Bajor brought about an end to the Dominion War. The treaty provided that the Female Changeling be handed over to Federation custody, the Cardassian Union be re-established independent of the Dominion and that its occupation by Dominion and Breen forces be ended, and that all Dominion ships and personnel in the Alpha Quadrant be withdrawn to the Gamma Quadrant.