He is best known for playing Meriadoc "Merry" Brandybuck in Peter Jackson's film trilogy The Lord of the Rings (2001–2003), and Charlie Pace on the ABC television drama Lost (2004–2010).

[4] In Stockport, he attended St Anne's Roman Catholic High School (where his uncle taught and later became head teacher) and Aquinas College, where he studied English literature, drama and geography.

After his second year at St Anne's, Monaghan became a regular in school plays such as Oliver Twist, A Christmas Carol and Bugsy Malone before joining the Manchester Youth Theatre.

[5][6][non-primary source needed] He made his feature-film debut as Russian sailor Sasha in the TV film Hostile Waters.

He was a regular cast member on the ABC series Lost from 2004 to 2007, playing English former rockstar and drug addict Charlie Pace.

[10][11] In 2010, Monaghan and US actress Megan Fox made an appearance as a couple in an abusive relationship in the music video for Rihanna and Eminem's song "Love the Way You Lie".

[12] In November 2012, a new show on Channel 5 titled Wild Things with Dominic Monaghan started airing in the United Kingdom.

The documentary shows Monaghan travelling to different locations such as Venezuela and Ecuador to film and interact with the exotic and often dangerous local wildlife.

[15] Monaghan is a contributing writer for the music and culture magazine Paste, primarily writing articles about Premier League football.

He was named as part of the cast for the last film in the sequel trilogy which is Star Wars: The Rise of Skywalker, reuniting with J.J. Abrams, a co-creator of Lost.

[17] Monaghan and castmate Billy Boyd started the podcast The Friendship Onion, where they talk about their time filming The Lord of the Rings.

He made his stage debut in 2024 with Lord of the Rings castmate Boyd in the Canadian production of Tom Stoppard's Rosencrantz and Guildenstern Are Dead.

The other, done by Kat Von D on the reality TV series LA Ink, is located on his lower right arm and reads "Luminous beings are we, not this crude matter", a quote from Yoda.

[26] Monaghan provided the inspiration for the naming of Billy Boyd's band Beecake after he sent his friend a picture of a cake covered in bees.