Ratnakar or Rathnakar is an Indian name derived from Sanskrit Ratna.

• Ratnakar, Sanskrit term for ocean or sea, specifically the Indian Ocean
• Ratnākara (9th century CE), Sanskrit poet
• Rathnakar (actor), Indian actor
• Ratnākaraśānti (10th to mid 11th century CE), Buddhist philosopher
• Ratnakar Hari Kelkar (1904–1985), reviser and translator of the Bible
• Kimmane Rathnakar, Indian politician from Karnataka
• Ratnakar Matkari (born 1938), Marathi writer
• Ratnakar Pai (1928–2009), Hindustani classical music vocalist of the Jaipur-Atrauli Gharana
• Ratnakar Pandey, a politician from India
• Ratnakar Bank, a scheduled commercial bank in Maharashtra
• Sangita Ratnakara, 13th century musicological text
• Dashyu Ratnakar, a 1962 Ollywood/Oriya film directed by Prabhat Mukherjee Dasyu Ratnakar
• Ratnakar (2019 film), a 2019 Assamese-language film by Jatin Bora

• Ratna (disambiguation)
• Kar (disambiguation)