The first Prime Minister of India was Jawaharlal Nehru, who held office from 1947 until his death in 1964. Nehru played a pivotal role in the Indian independence movement and was a close associate of Mahatma Gandhi. He became the leader of the Indian National Congress party and was appointed as the Prime Minister by the Governor-General of India, Lord Mountbatten, after India gained its independence from British colonial rule.

Key Achievements of Jawaharlal Nehru:
1. Architect of modern India: Nehru played a significant role in shaping India's post-independence policies and institutions. He emphasized the principles of secularism, democracy, and socialism, which are enshrined in the Indian Constitution.

2. Economic policies: Nehru implemented a mixed economy model with an emphasis on state-led industrialization. Under his leadership, India adopted the policy of planned economic development, which aimed at reducing poverty, promoting industrial growth, and improving the standard of living.

3. Non-alignment: Nehru was one of the key figures in the Non-Aligned Movement, which advocated for independence from both Western and Eastern blocs during the Cold War. He aimed to maintain India's autonomy and promote peace and cooperation among nations.

4. Educational reforms: Nehru prioritized education and launched various initiatives to improve literacy rates and establish educational institutions. He also championed scientific research and development, leading to the establishment of several scientific and technological institutions.

5. Foreign policy: Nehru played a crucial role in shaping India's foreign policy. He advocated for peaceful coexistence and non-interference in the internal affairs of other countries. He also worked towards resolving conflicts, including the Kashmir issue with Pakistan.

Successors of Jawaharlal Nehru:
After Nehru's death in 1964, Lal Bahadur Shastri became the second Prime Minister of India. Shastri led the country during the Indo-Pakistani War of 1965 and was known for his simplicity and integrity. However, his tenure was short-lived as he passed away in 1966.

After Shastri, Indira Gandhi, Nehru's daughter, became the third Prime Minister of India. She served as the Prime Minister from 1966 to 1977 and again from 1980 until her assassination in 1984. Indira Gandhi implemented various economic and social reforms, but her tenure was also marked by political controversies and the imposition of a state of emergency.

In conclusion, Jawaharlal Nehru was the first Prime Minister of India and played a significant role in shaping the country's policies and institutions. His successors, Lal Bahadur Shastri and Indira Gandhi, also made important contributions to India's political landscape.