Link's Cow is a character from The Legend of Zelda: Ocarina of Time. As the name implies, she is a cow under Link's ownership. Link can win her from Malon by beating the record for racing a lap around Lon Lon Ranch. Malon will automatically deliver her to Link's House in Kokiri Forest. Link can play Epona's Song for his cow to please her, and in return she will give Link a portion of Lon Lon Milk if he has an empty Bottle.
How Malon managed to get the cow up the ladder and into Link's House is never explained. Interestingly, Malon is able to get her into the house if Link beats the record before he completes the Forest Temple when Kokiri Forest is overrun by monsters.