Moondrezhuthu (transl. Three letters) is a 1968 Indian Tamil-language crime film, directed by T. R. Ramanna, produced by T. K. Ramarajan and written by T. N. Balu. Music was by T. K. Ramamoorthy.^[1] The film stars Ravichandran, Jayalalithaa, Srividya and Sheela. It was released on 10 May 1968.^[2]

The film revolves around a chest filled with valuable items and a handful of people competing for it. One character is a greedy old man Rajarathnam Pillai, whose daughter is Selvi. A manager Meganathan is trusted with the chest which needs to be handed over to its legitimate claimants (Pankajam and her suffering family). In his efforts to deliver the box to the rightful owners, he is forced to murder and is sent to jail. His son Maran, to whom he narrates the events, buries the treasure in a village and writes down the clues to find it on three different pieces of paper, with three different Tamil letters, தி (Thi) மு (Mu) and க (Ka).

After many twists and turns, the three villains decipher that the Tamil letters are a clue to the name of the village where the box is buried and they end up going there. Now, the land is in the possession of a factory coming up in its place, and another villain Karmegam also goes after the treasure by killing the others with heavy equipment. How the hero assisted by Nagesh deals with this forms the rest of the story. At the end, the villains are exposed and the box is handed over to its rightful owners. The lovers, Selvi and Maran, are united too.

Music was composed by T. K. Ramamoorthy and lyrics were written by Kannadasan.^[3][4]

Kalki criticised the film for its outdated storyline and lack of originality.^[5] Despite this, it became a success.^[6]