The film stars Vishal in the titular role, alongside Priya Bhavani Shankar in a dual role as the female lead and the hero's mother, Samuthirakani, Gautham Vasudev Menon, Yogi Babu, Murali Sharma, Hareesh Peradi, Mohan Raman and Vijayakumar.

It was shot sporadically in several legs, with filming locations including Thoothukudi, Trichy, Karaikudi, Vellore, Tirupati, Chennai, and wrapped by late-January 2024.

The music was composed by Devi Sri Prasad, while cinematography and editing were handled by M. Sukumar and T. S. Jay.

Rathnam was released on 26 April 2024 to mixed reviews from critics with praise for the cast's performance (especially Vishal), screenplay, and Devi Sri Prasad's background score and music, but criticized its excessive gore and violence, pacing, and writing due to its outdated feel.

Reportedly, the team was in talks with Sai Pallavi and Aishwarya Lekshmi to play the lead female role before finalising Priya.

[8] In early July, Devi Sri Prasad was chosen to compose the soundtrack and background scores for the film.

"[25] Manigandan KR of Times Now gave 3/5 stars and wrote "Rathnam is not a perfect commercial action entertainer.

"[27] Akchayaa Rajkumar of The News Minute gave 2/5 stars and wrote "Neither stellar performances from Priya Bhavani Shankar and Samuthirakani nor the plot twists towards the end would save the audience from the headache and potential ear damage that Rathnam might cause.

"[28] Kirubhakar Purushothaman of The Indian Express gave 1.5/5 stars and wrote "Vishal and Hari come together for an action-drama again, which is as dated as their old collaborations.

"[29] Anusha Sundar of OTTplay gave 1.5/5 stars and wrote "Even as Vishal stands tall and brings some action blocks to life, the caricature made out of his and other characters makes Rathnam a childish film.

"[30] Latha Srinivasan of Hindustan Times wrote "With old tropes and old action, Vishal and Hari are unable to capture the audience's attention with this one.

"[31] Bhuvanesh Chander of The Hindu wrote "In his latest outing with Vishal, Hari attempts to adapt some of his tropes to the sensibilities of the modern-day audience, but the ideas he plays around with and the story he wishes to tell still belong in the 2000s.

"[32] Ram Venkat Srikar of Film Companion wrote "With all the thoughts it wanted to blend, Rathnam could have been a lot more than what it ended up being.