Ida Rentoul Outhwaite, also known as Ida Sherbourne Rentouland Ida Sherbourne Outhwaite(9 June 1888 – 25 June 1960), was an Australian illustrator of children's books. Her work mostly depicted fairies.
Ida was born in Carlton, Victoria, the youngest child of four and second daughter of the Rev. Dr. John Laurence Rentoul, an Irish-born Presbyterian minister and academic, and his wife Annie Isobel (née Rattray). At the time of her birth Outhwaite's father was a professor at Ormond College, University of Melbourne, and later moderator-general of his church for 1912-14, and when the World War I broke out, chaplain-general of the Australian military forces.She was educated at Presbyterian Ladies' College, Melbourne.