Animated Films:
* Spirit: Stallion of the Cimarron (2002): A spirited wild stallion resists capture and finds his place in the wild.
* My Little Pony: The Movie (2017): The Mane 6 embark on a journey to find a magical artifact to save Equestria.
* The Last Unicorn (1982): A beautiful unicorn searches for others of her kind after learning she is the last one.
* Secret of NIMH (1982): A courageous mouse mother embarks on a perilous journey to find a cure for her sick son. (Features a talking horse named Justin)
* Black Beauty (1994): A beloved classic about a horse who experiences various owners and adventures.
* The Horse Whisperer (1998): A troubled girl and her injured horse find solace with a mysterious horse whisperer. (Animated version)
* Horseland (2003): A group of kids band together to save a local horse ranch.
* Bolt (2008): A dog who believes he's a superhero embarks on a cross-country adventure. (Features a talking horse named Mittens)
* Cloudy with a Chance of Meatballs (2009): A quirky scientist accidentally causes food to rain from the sky. (Features a talking horse named Earl)
* Brave (2012): A Scottish princess defies tradition and sets out on a journey to change her fate. (Features a magical horse named Angus)
* Ponyo (2008): A goldfish princess wishes to become human and falls in love with a human boy. (Features a horse-like fish called Ponyo)
* The Little Prince (2015): A young girl meets a mysterious pilot who tells her about a magical world. (Features a horse-like character called the Fox)
Live-Action Films:
* Seabiscuit (2003): The true story of the legendary racehorse Seabiscuit and his unlikely rise to fame.
* Black Beauty (1971, 1994, 2004): Multiple film adaptations of the classic novel.
* The Horse Whisperer (1998): A troubled girl and her injured horse find solace with a mysterious horse whisperer.
* National Velvet (1944): A young girl dreams of competing in the Grand National steeplechase.
* War Horse (2011): A horse's journey through World War I, from the fields of England to the battlefields of France.
* Flicka (2006, 2012): A teenage girl bonds with a wild mustang.
* The Man Who Loved Horses (1975): A film about a man who loves horses and spends his life training them.
* The Black Stallion (1979): A young boy befriends a wild stallion after being shipwrecked on a deserted island.
* My Friend Flicka (1943): A classic story about a boy's bond with a wild horse.
* The Horse in the Gray Flannel Suit (1968): A man adopts a wild horse and tries to tame it.
* The Horse Soldiers (1959): A Civil War film about a daring Union raid through Confederate territory.
* The Power of One (1992): A young boy's friendship with a horse helps him overcome racism and prejudice.
Documentaries:
* The Wild Horses of Nevada (2006): A documentary about the wild horses of Nevada and their struggle for survival.
* Equus: The Story of the Horse (2005): A documentary about the evolution of the horse and its relationship with humans.
* The Horse Whisperer (2001): A documentary about the real-life horse whisperers and their methods.
* The Horseman (2010): A documentary about the life of legendary horseman Buck Brannaman.
This is not an exhaustive list, but it should give you a good starting point for finding movies and cartoons about horses.