Gladys Lillian Moncrieff OBE (13 April 1892 – 8 February 1976) was an Australian singer who was so successful in musical theatre and recordings that she became known as 'Australia's Queen of Song' and 'Our Glad'.

Moncrieff was born in Bundaberg, Queensland. Her father Robert Edward Moncrieff was a piano tuner, and her mother, who went by the stage name Amy Lambell, was a professional singer; they lived in North Isis. She attended several schools in north Queensland, and quickly became involved in music. Her first stage performance was at the age of six at the Queen's Theatre in Bundaberg, where she sang the American folk song "The Merriest Girl That's Out" with her father accompanying on piano. She performed in Gilbert and Sullivan productions. At the 1907 Charters Towers eisteddfod, Gladys shared first prize for her junior soprano rendition of "O for the Wings of a Dove" with local girl Eileen Coleman.

When Moncrieff left school, she and her parents travelled around far north Queensland performing. Moncrieff was billed as 'Little Gladys: The Australian Wonder Child' and her performances helped her to raise funds to move to Brisbane to pursue her career. She worked in Brisbane and Toowoomba during 1909, and then went to Sydney with her mother. In Sydney she auditioned for Hugh J. Ward for a position in J. C. Williamson's theatre. She was successful, and with a starting salary of £3 per week she spent 18 months receiving singing lessons from Ward's wife, Madame Grace Miller. In January 1913 she had a small part in The Sunshine Girl at Her Majesty's Theatre, Sydney. In 1914 she was in the chorus of a house Gilbert and Sullivan production; for there she took on leading roles such as Josephine in H.M.S. Pinafore. The company toured New Zealand and performed in Melbourne.

Moncrieff toured South Africa and New Zealand as a leading lady in numerous productions. When she returned to Australia she landed her most famous role as Teresa in Harold Fraser-Simson's light opera The Maid of the Mountains, which she first performed in Melbourne in 1921. The waltz song "Love Will Find a Way" became particularly associated with her. The Maid was to become the most frequently revived musical of the Australian stage, and Moncrieff appeared in it some 2,800 times. She also was a success in A Southern Maid in 1923.

Contemporary critics wrote of the purity, richness, power and wide range of her voice, her conviction of style and her clear enunciation. H. Brewster-Jones spoke of the "richness of quality and expression in her well produced voice, and makes a striking appeal to a concert audience with her platform manner and interpretive abilities" in a 1938 review of a concert performance at the Adelaide Town Hall.

Her career was put on hold in March 1938 when she was involved in a motor vehicle accident, and she did not return to the stage until June 1940. She returned to perform in musical comedy, and was engaged to entertain Australian troops fighting in the Second World War at home and in New Guinea, and she became very active raising funds for war-related charities. In 1951 she toured Japan and Korea to entertain British and Australian occupation forces. For her wartime contributions, she was made an Officer of the Order of the British Empire in 1952 for services to patriotic and charitable movements.

She continued her stage and radio work, and during 1958 and 1959 began her farewell stage tour of Australia and New Zealand. Her final stage appearance was at Hamilton, New Zealand, and her last public performance was in a televised concert in Brisbane in 1962. She retired to the Gold Coast, Queensland in 1968 and prepared her memoirs My Life of Song which was ghosted by Lillian Palmer and published in 1971. In 1962 Moncrieff made guest appearances on George Wallace Jnr’s television show Theatre Royal.

Moncrieff came outside of her Gold Coast home on a canal to wave to the people on the canal cruise boats whilst they played her arias.