Catherine Martin Luhrmann AC (born 26 January 1965) is an Australian costume designer, production designer, set designer, and film producer, best known for her frequent collaborations with director Baz Luhrmann. She has received numerous accolades, including four Academy Awards, six BAFTA Awards, and a Tony Award. Martin was appointed a Companion of the Order of Australia in 2025.

Martin came to international prominence for providing both the costumes and production design on Strictly Ballroom (1992), Luhrmann's feature directorial debut which later became the first installment of the "Red Curtain Trilogy". She won both the Academy Award for Best Costume Design and the Academy Award for Best Production Design for her work on Curtain's final chapter Moulin Rouge! (2001). Martin became just the second woman to win multiple Oscars in a single year (after Edith Head) and the first to accomplish this feat twice, winning the same two categories for The Great Gatsby (2013). She was also Oscar-nominated for Romeo + Juliet (1996), Australia (2008), and Elvis (2022). Having won four awards out of nine nominations, she holds the record for the most Oscar wins of any Australian.

Martin was born on January 26, 1965, in Lindfield, New South Wales, to a French mother and an Australian father, both academics who met at the Sorbonne; her father was pursuing his expertise in 18th-century French literature, and her mother was studying mathematics at university. She and her brother grew up in Sydney but spent a lot of time with their grandparents in France's Loire Valley, visiting "every art gallery, every museum" along the way. Martin was fascinated from an early age by the vintage clothing parades occasionally thrown by her Australian grandmother and her church friends. She would beg her parents to take her to London's Victoria and Albert Museum so she could dig through the costume section, and recalled "being blown away by the costume gallery, being able to see a pleated lace ruff in reality" when she finally got there. Her mother taught her to use a sewing machine at age 6, and by age 15 she was creating her own patterns to make herself dresses. Martin cited The Wizard of Oz as her childhood inspiration and an extraordinary journey to take when she was 10, and then Gone with the Wind as the movie that, at age 13, changed her life from a fashion perspective.

Martin attended North Sydney Girls High School and, while a student, got a part-time job as an usherette at the Roseville theatre. She was first enrolled at Sydney College of the Arts and spent a year studying the visual arts before deciding to drop out for a career change. Then she studied pattern cutting at East Sydney Technical College. She was accepted into the National Institute of Dramatic Art (NIDA) and graduated in 1988 with a diploma in design. In her last year at university, she met and started collaborating with a fellow student, Baz Luhrmann, whom she later married. At that time, Luhrmann returned to NIDA looking for young designers with whom he planned to stage his one-act play, Strictly Ballroom, and Martin did some work on that production.

Martin's first professional engagement came after graduation when she began working on Luhrmann's environmental opera experiment, Lake Lost, staged at a television studio in Melbourne to celebrate the Australian Bicentenary in 1988. Their collaboration continued at Opera Australia when she provided set designs for Luhrmann's 1990 production of Giacomo Puccini's La bohème as well as the 1993 production of Benjamin Britten's A Midsummer Night's Dream.

Martin gained international acclaim when she entered the film industry, recreating her designs in Luhrmann's feature directorial debut, Strictly Ballroom (1992), the first part of the "Red Curtain Trilogy". It was a major financial success and received widespread acclaim from critics and audiences, who lauded the acting, direction, and production values. Among other accolades, the film cleaned up at the AFI Awards, picking up leading eight wins from 13 nominations and also winning three of its eight nominations at the BAFTAs, including both the Best Costume Design and the Best Production Design for Martin's visuals. She then received her first Oscar nomination for art direction in the trilogy's second installment, Romeo + Juliet (1996).

Their third feature film collaboration which concluded Curtain's Trilogy was Moulin Rouge! (2001). She earned both the Academy Award for Best Costume Design and the Academy Award for Best Production Design for her richly designed sets and dazzling costumes, which received widespread recognition from critics and audiences alike. She shared the former prize with Angus Strathie, the latter with Brigitte Broch (for the film's set decoration). Martin's double wins makes her just the second woman to win multiple Oscars in a single year, after fellow costume designer Edith Head.

For their next project together, the pair teamed up adaptating Luhrmann's earlier Australian production of La bohème for Broadway theatre, which opened to critical acclaim in December 2002. She won the Tony Award for Best Scenic Design and, alongside Strathie, was nominated for the Tony Award for Best Costume Design the following year.