T. K. Shanmugam (1912 – 1973; also known as "Avvai" T. K. Shanmugam) was a Tamil theatre and film artist. He acquired the prefix "Avvai" after portraying saint-poet Avvaiyar in a play.[1]

Kamal Haasan refers to him as his Guru and says this is where he learned acting. When Kamal Hassan starred as a woman, Avvai Shanmugi, in the Tamil adaptation of Hollywood blockbuster Mrs. Doubtfire, it was the actor's tribute to his teacher and thespian.

“He curved his lower lip inwardly to give a realistic image of an old woman without teeth. He even removed two of his teeth for the role,” says T.K.S. Kalaivanan, his son. “He had pain in his jaws for the rest of his life and the curved posture, holding a walking stick gave him constant back pain.”

His self-effacing autobiography Yenathu Nataka Vaazhkai , gives a panoramic view of the theatre from the beginning of the 20th century, the personalities involved in it, the plight of boys who were inducted into these troupes by their parent out of poverty, the social status of the actors and importantly the uncertain financial condition.

Actors such as N. S. Krishnan,K. R. Ramasamy , S. S. Rajendran, M. N. Rajam, director A. P. Nagarajan and one of the outstanding Carnatic vocalists T. M. Thiagarajan were some names associated with the TKS Brothers troupe. Later, it became T.K.S. Sabha and Mr. Kamal Hassan joined the troupe on the recommendation of film producer A. V. Meiyappan.

The TKS Brothers had close association with both the Communist and Dravidian movements. They used many of the songs of late communist leader Jeevanandam in their plays and it was Shanmugam who wrote a foreword for Annadurai's first novel, Kumasthavin Magal. As early as in 1943, T.K. Shanmugam described Annadurai as a future leader of the Tamils. In his autobiography, he had wondered how it occurred to him to call him so.

Cho Ramaswamy appreciated that his contributions to tamil stage are unparalleled.