[1][2] Born in Northern Ireland to an English mother and New Zealand father, Neill moved to Christchurch with his family in 1954.

He first achieved recognition with his appearance in the film Sleeping Dogs (1977), which he followed with leading roles in My Brilliant Career (1979), Omen III: The Final Conflict, Possession (both 1981), Evil Angels (also known as A Cry in the Dark) (1988), Dead Calm (1989), The Hunt For Red October (1990), The Piano (1993), and In the Mouth of Madness (1994).

Outside of film, Neill has appeared in numerous television series in guest and recurring roles, including Reilly, Ace of Spies (1983), The Simpsons (1994), The Tudors (2007), Crusoe (2008–2010), Happy Town (2010), Alcatraz (2012), and Rick and Morty (2019).

[6][7] His great-grandfather Percival "Percy" Neill had left Belfast for Australia, joining a firm of merchants in Melbourne.

[8][9][10] At the time of Neill's birth, his father was stationed in Northern Ireland, serving as an officer with the Royal Irish Fusiliers.

After a year, his parents and younger sister Juliet moved south to his father's home city of Dunedin.

[14] He went on to study at the University of Canterbury but was uncertain about a career, deciding not to follow his father into the army or the family firm.

He acted in a production of Marat/Sade by Mervyn Thompson, and when another actor dropped out of a Wellington season, Neill replaced him as Jacques Roux.

He transferred from Canterbury to Victoria University of Wellington to finish his Bachelor of Arts with a philosophy unit, and passed the "logic" paper with some last-minute coaching by John Clarke.

Neill played Macbeth in a university production directed by Phillip Mann, then joined Downstage as a professional paid actor for $25 per week, plus food from the kitchen left over from the meal served to the audience before the show.

[20] In 2004, on the Australian talk show Enough Rope, interviewer Andrew Denton briefly touched on the topic of Neill's stuttering.

He recalled how deeply it had affected him in his life and, as a result, he often found himself "hoping that people wouldn't talk to [him]" so he would not have to answer them.

He made some Australian films that were less widely seen: The Journalist (1979), Just Out of Reach (1979) and Attack Force Z (1981), and appeared in television productions such as Young Ramsay and Lucinda Brayford.

An early American starring role was in 1987's Amerika, playing a senior KGB officer leading the occupation and division of a defeated United States.

His leading and co-starring roles in films include the thriller Dead Calm (1989),[22] the two-part historical epic La Révolution française (1989) (as Marquis de Lafayette), The Hunt for Red October (1990), Death in Brunswick (1990)[22] (in which he was re-teamed with old friend John Clarke), Jurassic Park (1993),[25] Sirens (1994), The Jungle Book (1994), John Carpenter's In the Mouth of Madness (1995), Event Horizon (1997), Bicentennial Man (1999), the comedy The Dish (2000),[22] and Jurassic Park III (2001).

Neill has occasionally acted in New Zealand films, including The Piano (1993), Perfect Strangers (2003), Under the Mountain (2009), and Hunt for the Wilderpeople (2016).

In 1993, he co-starred with Anne Archer in Question of Faith, an independent drama based on a true story about one woman's fight to beat cancer and have a baby.

It has elements that are hard to beat: revenge and betrayal, lust and treason, all the things that make for good stories.

He played the role of Chief Inspector Chester Campbell, a sadistic corrupt policeman, who came to clean up the town on Churchill's orders.

[32] In 1980, Neill met actress Lisa Harrow while filming Omen III: The Final Conflict (1981) and they have a son.

[49][47] Neill was appointed an Officer of the Order of the British Empire in the 1991 Queen's Birthday Honours, for services as an actor.