Zlatko Šimenc (born 29 November 1938) is a retired Croatian water polo player of Slovenian origin. He was part of the Yugoslav teams that won a silver medal at the 1964 Olympics and placed fourth in 1960. He won three more medals at the European championships in 1958–1966.
Šimenc's parents moved from Slovenia to Croatia before he was born. They had three sons and one daughter, with Zlatko being the youngest child. He took up swimming aged 11, and in his twenties changed to water polo and handball. He trained as a water polo defender in the summer and as a handball striker in the winter, and won national titles in both sports with his club Mladost. Between 1955 and 1975 he played 101 water polo and 24 handball matches for the national Yugoslav teams.
In 1958, Šimenc enrolled to study law, but next year changed to the newly established in Zagreb institute of physical education, and graduated in 1966. He later earned a master's degree in social sciences and defended a PhD in kinesiology. Since 1966 until retirement he worked at the Department of Team Sports of the University of Zagreb, and published ca. 60 scientific papers and books on handball and water polo. In parallel he served as a sports official at the Yugoslav (1980–82) and Croatian (1992–96) water polo federations and was a member of the Croatian Olympic Committee (1991–95). His son Dubravko also became an Olympic medalist in water polo, while his daughter Iva is a coach and former competitor in synchronized swimming.