Step 1: Understanding the Question
The question asks to identify the person responsible for the initial construction (foundation) of the Great Stupa at Sanchi.
Step 2: Historical Context
The Great Stupa (also known as Stupa No. 1) at Sanchi is one of the oldest stone structures in India. Its original foundation was laid by the Mauryan emperor Aśoka the Great in the 3rd century BCE. It was initially a smaller brick stupa built over the relics of the Buddha. Later rulers, particularly during the Shunga dynasty, expanded it to its present form by encasing it in stone.
Step 3: Final Answer
The foundation of the Sanchi Stupa was laid by Emperor Aśoka.