Neeson was born, the son of Katherine "Kitty" (née Brown), a cook, and Barnard Neeson, a caretaker at the local Catholic boy's primary school. He was called Liam, the Irish equivalent to William, after the local priest. He was the third child in the family and the only boy among four siblings; his sisters are Elizabeth, Bernadette and Rosaline.

At age nine, Neeson began boxing lessons at the All Saints Youth Club. It was at age eleven that Neeson first stepped on stage. His English teacher gave him the lead role in a school play, which he accepted because the girl he fancied would be starring. From then on, he kept acting in school productions for the following years.

His interest in acting and decision to become an actor was also influenced by Ian Paisley whose church Neeson would sneak into. Neeson has said of Paisley that "He had a magnificent presence and it was incredible to watch this six foot-plus man just bible-thumping away...It was acting but it was also great acting and stirring too. And his Baptisms skills are second to none."

Still boxing at sixteen, he had been Youth Heavyweight Champion of Ireland for three consecutive years, aided by his height.

While at University, Neeson's abilities as a talented footballer emerged which resulted in him being spotted by Bohemian FC manager Seán Thomas. Neeson travelled to Dublin for a trial with the club, and featured briefly when he came on as a substitute in a game against Shamrock Rovers, replacing Tony O'Connell. Neeson was not offered a contract at the club and that remained his only performance in professional football.

After leaving university, Neeson returned to Ballymena and worked in a variety of small jobs, from fork-lift operator at Guinness to truck driver. He also worked at a teacher-training college in Newcastle for two years before again returning to his hometown.

Neeson would get his first film experience in 1973, playing Jesus Christ in the religious film, Pilgrim's Progress directed by Ken Anderson. After a bet from co-workers at the architects' office where he worked, Neeson applied for an audition at the Lyric Players' Theatre in Belfast.

After two years there, Neeson moved to Dublin and joined the Abbey Theatre in 1977. In 1980, film-maker John Boorman saw him on stage, acting as Lennie Small in Of Mice and Men, and offered him the part of Sir Gawain in the upcoming Arthurian movie, Excalibur.

After Excalibur, Neeson moved to London, where he continued working on stage, small budget movies and TV series. He lived with the actress Helen Mirren at this time, whom he met working on Excalibur. Between 1982 and 1987, Neeson starred in five films; mostly notably alongside Mel Gibson and Anthony Hopkins in 1984's The Bounty.

In 1987, Neeson made a conscious decision to move to Hollywood in order to star in high-profile roles. That year, he starred alongside Cher and Dennis Quaid in crime thriller, Suspect. The role would bring Neeson critics' applause, but it was 1990's Darkman that would bring his name to the public attention. Although the film gained success, Neeson's following years would not give him the same recognition.

In 1993, he joined Ellis Island co-star, and future wife, Natasha Richardson in the Broadway play, Anna Christie. (They also worked together in Nell, released the following year.) Director Steven Spielberg, impressed by his performance, offered him the coveted role of Oskar Schindler, in the upcoming film about The Holocaust, Schindler's List.

His critically acclaimed performance later earned him an Academy Award nomination for Best Actor; however, the award went to Tom Hanks for his performance in Philadelphia. Neeson also garnered BAFTA and Golden Globes nominations for Schindler's List.

Schindler's List established Neeson as a widely sought after leading actor. He later starred in period pieces Rob Roy (1995) and Michael Collins (1996), the latter earning him another Golden Globes nomination and a win for Best Starring Role at the Venice Film Festival. Neeson went onto star as Jean Valjean in the 1998 adaptation of Victor Hugo's Les Misérables and in The Haunting as Dr. David Marrow.

In 1999, Neeson took on the role as Obi-Wan Kenobi's mentor, Jedi Master Qui-Gon Jinn, in George Lucas' much anticipated Star Wars Episode I: The Phantom Menace. His voice would later be used in Episode II: Attack of the Clones. Neeson was to appear in the third prequel, Episode III: Revenge of the Sith as a Force Ghost, but a motorcycle accident prevented this and instead the character was mentioned only. Due to his height (6 ft 4 in/193 cm), Neeson cost George Lucas an additional $150,000 in set design on The Phantom Menace.

Neeson narrated the 2001 documentaries Journey Into Amazing Caves and The Endurance: Shackleton's Antarctic Adventure. After being nominated for a Tony Award for his role opposite Laura Linney in The Crucible, Neeson teamed up with Harrison Ford in Kathryn Bigelow's submarine thriller K-19: The Widowmaker (2002) as Captain Mikhail Polenin and appeared in Martin Scorsese's Gangs of New York (with Leonardo DiCaprio, Cameron Diaz and Daniel Day-Lewis).

He also played a recently widowed writer in Richard Curtis' ensemble comedy Love Actually (2003). His role as Alfred Kinsey in Kinsey again put Neeson up for nomination for a Golden Globe Award but he lost out to Leonardo DiCaprio for The Aviator.

In 2004, Neeson hosted an episode of the NBC sketch show Saturday Night Live. He starred as a redneck trucker, Marlon Weaver, in an "Appalachian Emergency Room" sketch and a hippie in a one-off sketch about two stoners (the other played by Amy Poehler) who attempt to borrow a police dog in order to find their lost stash of marijuana.

Despite vowing not to play any characters who were Irish stereotypes, Neeson did play a stereotypically Irish man named Lorken McArdle in the home makeover show parody "You Call This A House, Do Ya?" In 2005, Neeson could be seen playing Godfrey of Ibelin, in Ridley Scott's epic adventure Kingdom of Heaven, Henri Ducard/Ra's al Ghul in Christopher Nolan's Batman Begins and as Father Bernard in Neil Jordan's adaptation of Patrick McCabe's novel, Breakfast on Pluto.

Also in 2005, he voiced the role of a kindly priest on The Simpsons, who converted Bart and Homer to Catholicism. That same year, he gave his voice to the lion Aslan in the blockbuster fantasy film The Chronicles of Narnia: The Lion, the Witch and the Wardrobe. A year later, he narrated the documentary Black Holes: The Other Side of Infinity.

In 2007, Neeson starred in the American Civil War epic Seraphim Falls alongside Pierce Brosnan and Anjelica Huston. He is also set to star as Abraham Lincoln in a film directed by Steven Spielberg. In preparation for the role, Neeson visited Washington, D.C. and read Lincoln's personal letters. He also visited Ford's Theatre, where the President was shot.