The Fellowship of the Ring consisted of nine members. The company was formed to represent the nine companions against the nine Ringwraiths serving Sauron.
Its members were Frodo Baggins, Samwise Gamgee, Merry Brandybuck, Pippin Took, Aragorn, Boromir, Legolas, Gimli, and Gandalf. They came from several peoples and regions of Middle-earth, including Hobbits, Men, an Elf, a Dwarf, and a wizard.
The Fellowship was established at Rivendell after the Council of Elrond. Its mission was to help Frodo carry the One Ring toward Mordor, although the group later divided after the breaking of the Fellowship at Amon Hen. The number nine is therefore both a plot detail and a deliberate symbolic counterweight to the nine Nazgûl.