Tajuddin Ahmad (23 July 1925 – 3 November 1975) was a Bangladeshi politician. He led the first government of Bangladesh as its prime minister during the Bangladesh War of Independence in 1971, and is regarded as one of the most instrumental figures in the birth of Bangladesh.

Tajuddin began as a Muslim League youth worker in British India. He belonged to the Dhaka-based pro-democracy, secular Muslim League faction, which broke with the Muslim League's reactionary party line after the partition of India and the birth of Pakistan. As a member of the short-lived youth organisation, the Jubo League, he actively participated in the Language Movement in 1952. In 1953, he joined the Awami Muslim League (later the Awami League), a dissident offshoot of the Muslim League. The following year, he was elected a member of the East Pakistan Provincial Assembly. As a close confidant, he assisted Sheikh Mujibur Rahman in revitalising the Awami League into a secular political party during Ayub Khan's regime in the late 1960s.

As the General Secretary of the Awami League from 1966, Tajuddin coordinated the party during the tumultuous late 1960s and early 1970s, suffering imprisonment on several occasions. He formulated the early draft of the historic six-points demand that would eventually lead to the birth of Bangladesh. He coordinated the Awami League's election campaign for the 1970 Pakistani general election, in which the League gained a historic parliamentary majority. He also coordinated the non-cooperation movement of March 1971, precipitated by President Yahya Khan's delay in transferring power to the elected legislators. Tajuddin was among Sheikh Mujib's delegation in the Mujib-Yahya talks to settle the constitutional disputes between East and West Pakistan and transfer power to the elected National Assembly. Following the Pakistani army's crackdown on the Bangladeshi population on 25 March 1971, Tajuddin escaped to India. In the absence of Sheikh Mujib, he initiated the set up of the Provisional Government of Bangladesh in 1971 and headed it, operating in exile in India, as its prime minister.

In independent Bangladesh, Tajuddin served as the Minister of Finance and Planning in Sheikh Mujib's Cabinet from 1972 to 1974. He was also a member of the committee drafting the Constitution of Bangladesh. He resigned from the cabinet in 1974 to live a quiet life. Following Sheikh Mujib's assassination in a coup d'état, Tajuddin was arrested and assassinated on 3 November 1975, along with three senior Awami League leaders in prison.

Tajuddin Ahmad Khan was born on 23 July 1925 at Dardaria, which is a village in Dhaka District, Bengal Presidency, British India (now Gazipur District in Bangladesh), to Maulavi Muhammad Yasin Khan and Meherunnesa Khanam in a conservative, middle-class Muslim family. He was the eldest of nine siblings—three brothers and six sisters.

The Bengal province, the eastern frontier of India, consisted of two conceptual regions: West Bengal had a Hindu majority population and housed the provincial capital, Kolkata, a thriving centre of trade and culture; East Bengal, Tajuddin's home, was an impoverished hinterland of West Bengal, with a mostly poor Muslim peasant population. During Tajuddin's formative years, British rule in India was nearing its end, and Bengal was battered by famines, communal tensions, and other problems. It was a hotbed of anti-British activism. Against this backdrop, his political activism began at a very early age, sometimes interrupting his studies. The anti-British activists of Bengal were his earliest political inspiration.

After attending a few schools in Gazipur, Tajuddin moved to Dhaka, his district headquarters and the principal town in East Bengal, for further studies. In Dhaka, he went to Saint Gregory's High School, where he matriculated in 1944, securing 12th position in undivided Bengal. After matriculation, Tajuddin briefly lost interest in formal education because of his activism, pausing his studies for three years. At his mother's insistence, he resumed his studies and was admitted to Dhaka College. There he attended classes irregularly because of his activism. As a result, he could not take the Intermediate of Arts examination from there; instead, he took it from a private college as an irregular student in 1948 and passed, securing fourth position in East Bengal. He obtained a BA with honours in economics from the University of Dhaka. He also took his law degree from the University of Dhaka.

Tajuddin lost his father at age twenty-two and took over family responsibilities.