Julia Kathleen Nancy McKenzie CBE (born 17 February 1941) is an English actress, singer, presenter, and theatre director. She has premièred leading roles written by both Alan Ayckbourn and Stephen Sondheim. On television, she is known for her BAFTA Award nominated role as Hester Fields in the sitcom Fresh Fields (1984–1986) and its sequel French Fields (1989–1991), as Miss Marple in Agatha Christie's Marple (2009–2013) and for her appearance in the BBC One costume drama series Cranford.

McKenzie has also starred in numerous musicals, receiving a 1977 Tony Award nomination for her work in the Broadway revue, Side by Side by Sondheim. A six-time Olivier Award nominee, she has twice won the Olivier Award for Best Actress in a Musical; for the 1982 revival of Guys and Dolls and the 1993 revival of Stephen Sondheim's Sweeney Todd: The Demon Barber of Fleet Street. She also starred in the original London productions of the Sondheim musicals Follies (1987) and Into the Woods (1990). Her film appearances include Bright Young Things (2003) and Notes on a Scandal (2006).

McKenzie was born on 17 February 1941, in Enfield, Middlesex, England, the daughter of Kathleen Rowe and Albion McKenzie. She attended Woodside High School. She trained at the Guildhall School of Music and Drama.

McKenzie's early West End musical credits include Maggie May (1966), Mame (1969), and Company (1971). She appeared in the West End revue Side by Side by Sondheim in 1976, and made her Broadway debut when the show transferred to New York in 1977, receiving a Tony Award nomination for Best Featured Actress in a Musical. She also received a Drama Desk Award nomination. For her role as Miss Adelaide in the 1982 West End revival of Guys and Dolls, she won the first of two Olivier Awards for Best Actress in a Musical.

For her role in the 1986 West End production of the Alan Ayckbourn play Woman in Mind, McKenzie won the Evening Standard Award for Best Actress. She went on to appear in the original West End productions of two Stephen Sondheim musicals, playing Sally in Follies at the Shaftesbury Theatre in 1987, and the Witch in Into the Woods at the Phoenix Theatre in 1990. She continued her association with Sondheim when she starred as Mrs Lovett in the 1993 London revival of Sweeney Todd: The Demon Barber of Fleet Street. The role won her a second Olivier Award in 1994.

McKenzie appeared in a National Theatre 80th birthday tribute to Lord Olivier, Happy Birthday, Sir Larry, on 31 May 1987 in the presence of Olivier himself.

McKenzie's early television credits include the sitcom Maggie and Her (1978–1979), alongside Irene Handl and That Beryl Marston...! (1981), with Gareth Hunt. She went on to greater popularity with British viewers as Hester in the 1980s sitcom Fresh Fields opposite Anton Rodgers, and its 1990s sequel French Fields, for which she was voted TV Times Favourite Female Comedy Performance for five consecutive years. The role also earned her a 1985 BAFTA nomination for Best Entertainment Performance. She appeared as Mrs Forthby in Blott on the Landscape and as a villager involved in a series of murders in an episode of Midsomer Murders. Film credits include Hotel du Lac (1986), Shirley Valentine (1989), Bright Young Things (2003), These Foolish Things (2006) and Notes on a Scandal (2006).

She was the subject of This Is Your Life in 1981 when she was surprised by Eamonn Andrews outside the Royalty Theatre in London.^{[citation needed]}