Ramasamy Ganesan (17 November 1920 – 22 March 2005), better known by his stage name Gemini Ganesan, was an Indian actor who worked mainly in Tamil cinema. He was referred as Kaadhal Mannan (King of Romance) for his romantic roles in films. Ganesan was one of the "three biggest names of Tamil cinema", the other two being M. G. Ramachandran and Sivaji Ganesan. While Sivaji Ganesan excelled in dramatic films and M. G. Ramachandran was popular as an action hero, Gemini Ganesan was known for his romantic films. A recipient of the Padma Shri in 1971, he had also won several other awards including the Kalaimamani, the MGR Gold Medal, and the Screen Lifetime Achievement Award. He was one of the few college graduates to enter the film industry then.

Gemini Ganesan made his debut with Miss Malini in 1947 but was noticed only after playing the villain in Thai Ullam in 1952. After playing the lead role in Manam Pola Mangalyam (1953), he finally acquired star status. However, unlike Sivaji Ganesan or Ramachandran, Gemini Ganesan was not a stage performer and was never involved in politics. In his long film career spanning over five decades, Ganesan acted in more than 200 films. His performances on the screen were enhanced by successful playback singers such as A. M. Rajah and P. B. Sreenivas. Despite his celebrated film career, Ganesan's personal life, particularly his marriages to multiple women over the years, including famous Indian actress Savitri, has often been a subject of criticism. He had eight children, including actress Rekha.

Gemini Ganesan was born as Ramasamy Ganesan in 1920. He is the son of Ramaswamy Iyer and Gangammal, from a Tamil Brahmin family of Pudukkottai. Ganesan's paternal grandfather, Narayanaswami Iyer, was the principal of the Maharajah's College, Pudukkottai. After the death of his first wife, Narayanaswami had a second marriage with Chandramma, a devadasi who worked as a musician and dancer in a local Hindu temple. Notable among Narayanaswami Iyer's children with Chandramma were Muthulakshmi and Ramaswamy Iyer, the father of Gemini Ganesan.

When Ganesan was in the sixth grade, his grandfather died, and not long after that, his father also died. Meanwhile, Muthulakshmi (now known as Muthulakshmi Reddy) had studied well and become a doctor; she was affluent and educated and had thoroughly abandoned the style of life followed by her mother and maternal ancestors, so much so that she became the leader of a social reform movement aimed at eradicating the Devadasi system. She was instrumental in ensuring the passage through parliament of the Devadasi Abolition Act. After the death of his father, Ganesan and his mother Bhagirathi moved to his aunt Muthulakshmi's home in Madras (now known as Chennai).

Muthulakshmi provided shelter to her mother Chandramma and also to Bhagirathi and Ganesan, but she was very dismissive and insulting towards her destitute relatives, and she felt ashamed of them because of their background as nautch girls.^{[citation needed]} She heaped many insults on the two widowed women and ensured that they did not show their faces to any guests who visited the house. Unhappy with the situation, Chandramma and Bhagirathi returned to Pudukkottai. However, they left Ganesan with his aunt, so he would grow into an educated and respectable man.^{[citation needed]}

Since Muthulakshmi was an ardent follower of Ramakrishna, she decided to enroll Ganesan into Ramakrishna Mission Home. While there, he was taught yoga and languages and was made to read the Bhagavad Gita. However, he could not bear being separated from his mother, who was in Pudukkottai, so he returned to his native place and studied at a high school there. Later on, he joined Maharajah's College, located in the same place. However, he completed his graduation from Madras Christian College, Chennai.

Ganesan's dream was to become a doctor. In April 1940, he went to Trichinopoly (now Tiruchirappalli) to see T. R. Alamelu. Alamelu's father proposed to his daughter in marriage and promised him a medical seat after graduation. Ganesan immediately agreed and married Alamelu in June 1940. Alamelu lost her father and elder sister within one month of her marriage. Ganesan's dreams of becoming a doctor were shattered. There was no choice left for him but to find a job immediately, as he was the only person to support his family. He got an interview from the Indian Air Force. Much against Alamelu's wishes, Ganesan went to Delhi. There, he met his uncle Narayanaswami who advised him to become a teacher. Finally, Ganesan worked as a lecturer in the Chemistry department of Madras Christian College. Later in 1947, he obtained work as a production executive in Gemini Studios, from where the title "Gemini" became prefixed to his name. He debuted in film from the casting department of the Studio itself.

From the casting department, Ganesan made his film debut in 1947 with the satire Miss Malini, in a minor role. The film, which was based on a story by R. K. Narayan, and cast him alongside his future Mistress Pushpavalli, was a box office failure as it was considered "ahead of its time", but was well received by intellectuals. No print of that film is known to survive, making it a lost film. This was followed by Chakradhari, in which he played another minor role as the Hindu god Krishna. The film was a box office success, but his performance went unnoticed. It was not until 1953 when he played a negative role in Thai Ullam, did people take notice of him as an actor. The next year, he appeared in a supporting role in the Gemini Studios film Moondru Pillaigal, which was unsuccessful. He was then cast as a hero for the first time with Manam Pola Mangalyam. The film, which featured him in a dual role, paired him with his future wife Savitri, and became a "milestone in his life". From then on, he carved out a niche for himself in Tamil cinema with films that favored romance over action.