Gabriel Oak, known as Samson Oak in some language versions, is a character from the Pokémon Sun & Moon anime series who serves as the director of the Pokémon School on Melemele Island in the Alola region. He is the cousin of the renowned Professor Samuel Oak from the Kanto region, and the two bear a striking physical resemblance that often leads people to mistake them for twins. Unlike his cousin's more formal attire, Gabriel Oak has a sun-tanned complexion and longer, dark beige hair which he wears past his shoulders. His typical outfit consists of a short-sleeved green shirt featuring silhouettes of a Pokémon such as Wailmer along with white wavy lines, paired with white shorts and purple sandals.

In terms of personality, Gabriel Oak is an upbeat and cheerful individual who is well-known for his love of Pokémon-themed humor. He frequently makes jokes and performs facial expressions or gestures imitating various Pokémon, though these comedic attempts rarely elicit laughter from those around him. This jovial yet often unappreciated sense of humor is one of his most defining characteristics, setting him apart from his more serious cousin from Kanto.

Within the story, Gabriel Oak is responsible for overseeing the Pokémon School that the protagonist Ash Ketchum attends upon arriving in Alola. He appears for the first time when Ash's mother, Delia Ketchum, delivers a Pokémon Egg to him on behalf of Professor Oak. He then formally welcomes Ash and introduces him to the school's other students. In his role as an instructor, he teaches students about the concept of regional forms, using the Alolan Exeggutor as a prime example to demonstrate the differences from its Kanto counterpart.

Gabriel Oak develops several key relationships throughout the series, most notably with his students including Ash, Lillie, and the others attending his school. He also shares a notable connection with his cousin, as the two meet when the Alola school visits the Kanto region to celebrate an anniversary, a moment that surprises the Rotom Pokédex due to their uncanny resemblance. As a Pokémon trainer, Gabriel Oak is partnered with a Komala that has a habit of ringing the school's bell and occasionally attacking its owner without warning. Together, this pair participates in and wins the Pokémon Pancake Race, an Alolan event requiring competitors to navigate obstacles while carrying a stack of pancakes. He also receives a Pokémon Egg from Professor Oak, which later hatches into a Kantonian Vulpix that knows the move Ember. He decides to keep and care for this Vulpix himself.

Gabriel Oak shows development in his capacity as a caretaker and educator, taking responsibility for one of the two eggs placed in his students' care and trusting them with the other. His abilities as a researcher are focused on the study of regional variants of Pokémon that have taken root in Alola. He is also a capable competitor, as demonstrated by his victory in the pancake race alongside his Komala.