There is giant subterranean fungi in the northwest forests of the US that are at least that old, according to a National Geographic article I read a few years ago.
As to sentient animals, I’ve encountered 5-foot long, 1,500lb Leatherback sea turtles here in the Caribbean while both diving and walking the beaches. Depending on who you talk to, their lifespan is anywhere from 50 to 400 years. The locals here laugh at the 50-year estimation, as a lot of their folklore is based on the longer of the estimations.
An interesting anecdote: In his later years, the extremely gifted English playwright, composer, director, actor and singer, Noël Coward certainly believed in the 400 year lifespan. Always looking for a way to enhance his own lifespan and virility, he would get injections of Leatherback sera derived from some organ in the Leatherback (he also received goat injections for the same reason). He lived hard and fast, and was fanatically private about his lifestyle, but only made it to 74. His longtime secretary and companion published a tell-all, but loving biography once Coward was safely in the grave. He swears that the effects of the injections lengthened both his lifespan and his virility by counteracting the effects of his active lifestyle and estimates Coward would have never made it beyond his forties without them. This isn’t good science, of course, but the intelligence in which Coward lived his life lends a modicum of credence to his choice of medicines. But mostly, it’s just an interesting anecdote about a fascinating man.