Woodstock is a fictional character in Charles M. Schulz's comic strip Peanuts. He is a small yellow bird of unknown species and Snoopy's best friend. The character first appeared in the March 4, 1966, strip, though he was not given a name until June 22, 1970. He is named after the Woodstock festival of 1969.

Snoopy wordlessly interacted with a hummingbird, using only punctuation and musical notes, as early as 1951. In the early 1960s, Snoopy began befriending birds when they started using his doghouse for various purposes: a rest stop during migrations, a nesting site, a community hall, or a place to play cards. None of these birds were ever given a name, although they did, on occasion (e.g., July 10, 1962), use speech balloons, lettered in what would become the classic 'chicken scratch marks' of Woodstock's utterances. What set Woodstock apart from all these earlier birds was that he attached himself to Snoopy and assumed the role of Snoopy's sidekick and assistant. There had been no recurring relationships between Snoopy and the earlier birds who visited the yard of the Browns, and Snoopy was more often than not more hostile than friendly toward those birds.

In the Peanuts daily comic strip on March 3, 1966, a mother bird flew in while Snoopy was lying on top of his doghouse, nested on top of his stomach and flew away. Soon afterward two chicks hatched in the nest, one of which hung around Snoopy throughout the spring, and returned the following spring on April 4, 1967. Schulz began to establish character traits for Snoopy's new friend by revealing that he could talk (or at least emote), that he didn't like flying south every winter, and that he struggled with flying. By the end of this four-strip sequence, Snoopy, in character as the World War I Flying Ace, learns that the bird is his new mechanic, Woodstock's first supporting role.

After this introduction, the unnamed Woodstock is seen with Snoopy on occasion, and other birds continue to appear as they had for years. But Woodstock is singled out as the bird who befriended Snoopy, in part by continuing references to him as the Flying Ace's mechanic (July 12, 1967; June 12–14, 1968). On June 14, 1968, 14 months after his first landing on Snoopy and after a second appearance as a supporting character for Snoopy (his wrist wrestling partner on April 25, 1968), the most important aspect of Woodstock's relationship with Snoopy is made clear: Snoopy first refers to this bird as his buddy. This identification was more than enough for readers to know if they hadn't already figured it out, that this little bird, name or no name, had assumed the role of a regular character in the Peanuts cast.

Schulz did not give him a name until June 22, 1970. Schulz acknowledged in several print and TV interviews in the mid-1970s that he took Woodstock's name from the rock festival. (The festival's logo shows a bird perched on a guitar.)

Woodstock is a bird who is Snoopy's best friend. The only non-bird character who can understand Woodstock's speech is Snoopy. When depicted in the comic strip, his speech is rendered almost entirely in "chicken scratch" marks, with Snoopy's either directly translating or allowing the reader to deduce Woodstock's meaning in the context of Snoopy's replies. Woodstock does make nonverbal noises such as yawns, laughter, sighs and "Z"s or snores to indicate sleep. He also uses punctuation marks like "!" or "??" to indicate emotions. In the movies and television specials, the chicken scratches are rendered audibly as a staccato series of high-pitched honks and squawks by Snoopy's voice actor Bill Melendez. Woodstock often works as Snoopy's secretary (most notably when the latter was appointed "Head Beagle"), and caddies for him when he plays golf (usually with some difficulty). Woodstock also plays American football with Snoopy, usually attempting to catch the ball but, due to his size, he is simply hit by it; sometimes getting embedded into the ground a short distance.

Woodstock is a small and good-hearted yellow bird. He resourcefully wins the river rafting race in Race for Your Life, Charlie Brown after all other contestants have been eliminated. He routinely takes Snoopy's gentle verbal digs and practical jokes in stride, though he does not hesitate to stand up to Snoopy if his friend goes too far. Once, he and Snoopy stopped speaking to each other because of Snoopy's practice of reading War and Peace one word per day. When told that Woodstock was being attacked by the cat next door, Snoopy immediately rushed to his aid, getting clobbered in the process (what the cat was attacking ended up being a yellow glove). He also hates being mistaken for the wrong species of bird (though we are never told what species he actually is), and he is reluctant to eat thrown bread crumbs because he doesn't want anyone to think he's on welfare, and when asked about his net income by Snoopy in his 'census-taker' persona, he replied "four worms a day". He's a whiz at playing trivia too, and almost always manages to stump Snoopy.

Woodstock is also a skilled whistler. In the TV special, She's a Good Skate, Charlie Brown, when Peppermint Patty's music for a skating competition fails to play due to a malfunction that cannot be repaired expediently, Woodstock steps up to the microphone and whistles a flawless O Mio Babbino Caro, to which Peppermint Patty performs her routine. He also whistles his part in the song "The Best of Buddies" (via an instrumental version entitled "Woodstock's Samba") in the feature film Snoopy Come Home.