With a career spanning more than sixty years, he is noted for his roles on the screen and stage in genres ranging from Shakespearean dramas and modern theatre to popular fantasy and science fiction.

After his coming out as gay to his stepmother, Gladys McKellen, who was a Quaker, he said, "Not only was she not fazed, but as a member of a society which declared its indifference to people's sexuality years back, I think she was just glad for my sake that I wasn't lying any more".

At that young age he was already giving performances that have since become legendary such as his Justice Shallow in Henry IV alongside Trevor Nunn and Derek Jacobi (March 1959), Cymbeline (as Posthumus, opposite Margaret Drabble as Imogen) and Doctor Faustus.

[28] McKellen made his first professional appearance in 1961 at the Belgrade Theatre in Coventry, as Roper in A Man for All Seasons, although an audio recording of the Marlowe Society's Cymbeline had gone on commercial sale as part of the Argo Shakespeare series.

[29] One of McKellen's first major roles on television was as the title character in the BBC's 1966 adaptation of David Copperfield, which achieved 12 million viewers on its initial airings.

From 1978 to 1979 he toured in a double feature production of Shakespeare's Twelfth Night, and Anton Chekov's Three Sisters portraying Sir Toby Belch and Andrei, respectively.

The film spans nearly 20 years from the early 1940s to the 1960s, around an Englishwoman's experiences as a fighter for the French Resistance during World War II when she has a one-night stand with a British intelligence agent.

McKellen received mixed reviews from critics in particular Frank Rich of The New York Times who praised him for his "bravura and athletically graceful technique that provides everything except, perhaps, the thing that matters most—sustained laughter".

McKellen stars in the title role alongside an ensemble cast including Annette Bening, Robert Downey Jr., Jim Broadbent, Kristen Scott Thomas, Nigel Hawthorne and Dame Maggie Smith.

Laurie Winer from The Los Angeles Times wrote, "Even if he is preaching to the converted, McKellen makes us aware of the vast and powerful intolerance outside the comfortable walls of the theatre.

[50] McKellen portrayed a fugitive Nazi officer living under a false name in the US who is befriended by a curious teenager (Brad Renfro) who threatens to expose him unless he tells his story in detail.

That same year, he played James Whale, the director of Frankenstein in the Bill Condon directed period drama Gods and Monsters, a role for which he was subsequently nominated for the Academy Award for Best Actor, losing it to Roberto Benigni in Life is Beautiful (1998).

[24] In 1995, he appeared in the BBC television comedy film Cold Comfort Farm starring Kate Beckinsale, Rufus Sewell, and Stephen Fry.

[52] McKellen returned to the Broadway stage in 2001 in an August Strindberg play The Dance of Death alongside Helen Mirren and David Strathairn at the Broadhurst Theatre.

In 2003, McKellen made a guest appearance as himself on the American cartoon show The Simpsons in a special British-themed episode entitled "The Regina Monologues", along with the then UK Prime Minister Tony Blair and author J. K. Rowling.

In 2007, McKellen narrated the romantic fantasy adventure film Stardust starring Charlie Cox and Claire Danes, which was a critical and financial success.

That same year, he lent his voice to the armoured bear Iorek Byrnison in the Chris Weitz-directed fantasy film The Golden Compass based on the acclaimed Philip Pullman novel Northern Lights and starred Nicole Kidman and Daniel Craig.

[58][59] From 2013 to 2014, McKellen and Stewart starred in a double production of Samuel Beckett's Waiting for Godot and Harold Pinter's No Man's Land on Broadway at the Cort Theatre.

Variety theatre critic Marilyn Stasio praised the dual production writing, "McKellen and Stewart find plenty of consoling comedy in two masterpieces of existential despair".

There are ongoing jokes about McKellen's career as a relatively unsuccessful character actor who owns a tux because he stole it after doing a guest spot on "Downton Abbey" and that he holds the title of "10th Most Popular 'Doctor Who' Villain".

Liz Shannon Miller of IndieWire noted while the concept seemed, "weird as hell", that "Once you come to accept McKellen and Jacobi in a multi-camera format, there is a lot to respect about their performances; specifically, the way that those decades of classical training adapt themselves to the sitcom world.

[68] In October 2015, McKellen appeared as Norman to Anthony Hopkins's Sir in a BBC Two production of Ronald Harwood's The Dresser, alongside Edward Fox, Vanessa Kirby, and Emily Watson.

[80] In 2019, he reunited with Condon for a fourth time in the mystery thriller The Good Liar opposite Helen Mirren, who received praise for their onscreen chemistry.

[83][84] Since November 2021, McKellen and ABBA member Björn Ulvaeus have posted Instagram videos featuring the pair knitting Christmas jumpers and other festive attire.

[104] McKellen became an ordained minister of the Universal Life Church in early 2013[105] to preside over the marriage of his friend and X-Men co-star Patrick Stewart to the singer Sunny Ozell.

While McKellen had made his sexual orientation known to fellow actors early on in his stage career, it was not until 1988 that he came out to the general public while appearing on the BBC Radio programme Third Ear hosted by conservative journalist Peregrine Worsthorne.

In a statement on his website regarding his activism, the actor commented: I have been reluctant to lobby on other issues I most care about—nuclear weapons (against), religion (atheist), capital punishment (anti), AIDS (fund-raiser) because I never want to be forever spouting, diluting the impact of addressing my most urgent concern; legal and social equality for gay people worldwide.

[122] In 2010, McKellen extended his support for Liverpool's Homotopia festival in which a group of gay and lesbian Merseyside teenagers helped to produce an anti-homophobia campaign pack for schools and youth centres across the city.

McKellen said he opted to help save the building as it was the last theatre he played in New Zealand (Waiting for Godot in 2010) and the locals' love for it made it a place worth supporting.

[135] A recording of McKellen's voice is heard before performances at the Royal Festival Hall, reminding patrons to ensure their mobile phones and watch alarms are switched off and to keep coughing to a minimum.