Fangorn:

The eldest of the Ents and one of only three remaining from the First Age: Only three remain of the first Ents that walked in the woods before the Darkness: only myself, Fangorn, and Finglas and Fladrif- to give them their Elvish names; you may call them Leaflock and Skinbark if you like that better. (LOTR.496)

Fangorn rescued Merry and Pippin when they escaped the orcs that had carried them across Rohan. Later their news caused Fangorn to call an Entmoot at which it was decided to march on Isengard. Fangorn also directed many of the Huorns to raise the siege on Helms Deep.

In the First Age, it is believed that Fangorn walked the forests of Beleriand. At least, his chanting suggests a familiarity with the regions of Dorthonion, Neldoreth, Ossiriand, and Tasarinan.