A delegate was a diplomatic official who represented a government, species, or group for a conference, meeting, or peace talks. A group of delegates was called a delegation, or diplomatic corps, and may be made up of individuals such as ambassadors, aides and assistants.
In 2268, the USS Enterprise was tasked with ferrying 114 delegates to the Babel Conference. The Vulcans were the last represented species to be picked up. (TOS: "Journey to Babel")
When the USS Enterprise visited Gideon in 2269, Captain James T. Kirk noted in his captain's log that the Federation's "treaty negotiations have been difficult because Gideon has consistently refused the presence of a delegation from the Federation on its soil." (TOS: "The Mark of Gideon")
In 2364, the USS Enterprise-D transported a delegation of Antican and Selay to Pacifica. The lead Antican, Badar N'D'D, held the title of chief delegate. (TNG: "Lonely Among Us")
In 2366, a delegation of Ferengi beamed aboard the Enterprise to take part in the negotiations for control of the Barzan Wormhole. (TNG: "The Price")
Later that year, the Enterprise later transported a delegation of Legarans. (TNG: "Sarek")
In 2368, the Enterprise transported a delegation of Ullians to Kandra IV. (TNG: "Violations")
In 2370, the Enterprise transported a delegation of Cairn. The lead Cairn, Maques, was described as the delegation's "senior diplomat". (TNG: "Dark Page")