According to the Encyclopedia of Arda, the Rangers of Ithilien are "[a] force of the soldiers of Gondor, selected from the descendants of the people who had dwelt in Ithilien before it fell from Gondor's control. Dressed in camouflaging green and brown, they crossed the Anduin in secret to harass the forces of the Enemy in Gondor's old domain."
In the Lord of the Rings Online game, the Rangers of Ithilien is a kinship devoted to its members and to nonmembers.
We are the wanderers of Middle Earth; the wilderness and the woods is where you will likely discover us. Sent by Faramir, Captain Terrant Hawkeye, along with a company of Rangers clad in greens, browns, and with bows and swords, had made their way north to offer aid to the free peoples of the land. Originally made up of men alone, Elves, Dwarves, and even Hobbits have come to call themselves brothers and sisters of the land of Ithilien, now almost lost to the realm of Mordor. The Rangers of Esteldin and Tinnudir have welcomed the Ithilien Rangers and presented before them tasks. Will you take up the call and help in the defense of the north? Or will other lands suffer the same fate of Ithilien, in the strong grip of the evil realm of Mordor?