Seamus Finnigan is a fictional character from the Harry Potter Universe.
Seamus Finnigan is a wizard born to a Muggle father and a pure-blood witch mother. He attended Hogwarts School of Witchcraft and Wizardry the same year as the famous Harry Potter did and was sorted into Gryffindor House. He shared a dormitory with Harry, Ron Weasley, Dean Thomas, and Neville Longbottom, but it was with Dean he became best friends. He joined Dumbledore's Army in his fifth year. Seamus apparently had a close relationship with his parents as he believed his mother, who was a regular reader of the Daily Prophet, when she thought Voldemort had not truly returned, despite Harry Potter's claims. His favorite Quidditch team is Ireland's Kenmare Kestrels. He seemed to have a very large interest in Quidditch and tried out for Chaser for the Gryffindor team in his sixth year, but failed to get the position.
In the film adaptations, it is a running gag that Seamus keeps setting things on fire and causing them to explode.
 The Philosopher's Stone
Seamus attended his first year at Hogwarts the same year that Harry Potter did. He was sorted into Gryffindor and shared a dorm with Harry, Ron Weasley, Dean Thomas, and Neville Longbottom. He and Dean easily became very good friends. At the Welcoming Feast, he asked Sir "Nearly Headless" Nicholas, the Gryffindor ghost, how you could be nearly headless. Sir Nicholas demonstrated by detaching his head from his body, but the head still remaining partly hinged to it.
During Charms class on the morning of Halloween, Seamus managed to explode his and Harry's feather when practicing the Hover charm. He was a supporter of Harry and the rest of the Gryffindor Quidditch team during their first match, and joined his fellow first year Gryffindors in the top seats of the bleachers. He was impressed, along with many others, at how Harry had managed to remain on his broom during the match when Professor Quirrel tampered with it. Seamus lent his Wizard's Chess pieces to Harry to learn the ropes of the game over Christmas vacation, and departed to go home for the break.
 The Chamber of Secrets
In the second book and film, Seamus would be entering his second year at Hogwarts. During one Defence Against the Dark Arts lesson, Professor Lockhart showed the class a cage of Cornish Pixies. Seamus asked if they were harmful, and rather than answering him straightly, Professor Lockhart released them from the cage, the result being the pixies attacking the classroom. Seamus fled from the classroom as to avoid remaining in the room with them and recollecting them. He also joined Lockhart's Duelling Club and discovered that Harry could speak Parseltongue.
 The Prisoner of Azkaban
At Diagon Alley, with Dean Thomas, Seamus along with many others marveled over the new Firebolt in a store display window. During a Potions lesson, Seamus informed Harry and Ron that supposed mass murderer Sirius Black had broken free from his prison cell from Azkaban. He also had his say on whether or not Harry's tea dregs resembled a Grim, saying that from one side it indeed looked like a Grim, but from the other it somewhat resembled a donkey. In their first Defence Against the Dark Arts class, Professor Lupin brought in a Boggart wardrobe for the class to use. When Seamus went forth to participate, his Boggart turned out to be a very shrewd-looking banshee. He successfully used the Riddikulus spell on the banshee and in turn received five points for Gryffindor from Professor Lupin.
Seamus admired the anonymously-sent Firebolt Harry received and served as a guard for it. Amongst many others, Seamus was very upset to see Professor Lupin leave from his position as teacher at Hogwarts.
 The Goblet of Fire
During the summer before his fourth year, Seamus went to watch the Quidditch World Cup, in which Bulgaria and Ireland were matched up against each other. Seamus supported Ireland, of course, most likely because he was Irish. Seeing as they had no choice after noting the shamrocks all over Seamus's and his mother's tent, Harry, Hermione, and Ron agreed that they were also supporting Ireland. Seamus bought a rosette that said the players on Ireland's team. Seamus went with fellow fourth year Gryffindor, and most likely good friend, Lavender Brown to the Yule Ball.
 The Order of the Phoenix
Seamus and Harry had a row about how Harry claimed that Lord Voldemort had returned, Seamus saying that his mother, a regular reader of the Daily Prophet, believed what the paper was writing about him. The two avoided each other and did not speak to each other, except to retort at another. However, once Harry's interview in The Quibbler released and Seamus read it, he finally believed Harry and apologized to him. He joined Dumbledore's Army and managed to conjure up a Patronus at his first meeting, but it dissolved very soon after. He and a few others escaped the Room of Requirement when they discovered Dolores Umbridge and her Inquisitorial Squad were coming their way after Marietta Edgecomb blew their cover.
 The Half-Blood Prince
In his sixth year, Seamus as well as best friend Dean Thomas tried out for the position as Chaser for the Gryffindor Quidditch team. He was disappointed when he hadn't made the cut, and angry when Harry went to Dean to be Chaser when Katie Bell was away at St. Mungo's after brushing over a cursed necklace. He also marveled over the fact that Harry had already experienced Side-Along-Apparition and, as well as many others, told him to describe the feeling. Seamus claimed that he couldn't wait to be able to Apparate to get back at his cousin, Fergus, who would Apparate just to annoy him. Toward the end of the year, Dumbledore had been murdered by Severus Snape, and Seamus refused to leave the school before Dumbledore's funeral. The result ended in being that his mother finally allowed him to attend the funeral.
 The Deathly Hallows
Seamus returned to Hogwarts for his seventh and final year, despite his mother wanting him to return home towards the end of the previous year. When he returned, the school was controlled by Death Eaters and seemed much different. His best friend, Dean Thomas, had not returned to school for his seventh year, much to Seamus's displeasure, due to no proof that he has any wizard blood since his mother is Muggle and his father is dead. He remained loyal to Dumbledore's Army and helped fight in the Battle of Hogwarts. Neither Dean or Harry recognized Seamus until he spoke his very distinct Irish accent after he had been so badly scarred and bruised. When Dean returned to Hogwarts, Seamus ran to hug him after missing his presence throughout the year.
 Battle of Hogwarts
Seamus, along with a few others, saved Harry, Hermione, and Ron's necks after they had been hunted down by Dementors by conjuring up Patronus charms. His Patronus had finally been distinct, and it took the form of a fox. Seamus and Hannah Abbott were saved by Harry when Voldemort aimed a curse their way.
It is most likely that Seamus survived the battle, but his life after is unknown.