Concept:
Lothal is an important archaeological site of the Indus Valley Civilization.
It is located in Gujarat and is famous for its dockyard, town planning, bead-making industry, and trade connections.
Step 1: Identify Lothal.
Lothal was one of the important centres of the Harappan civilization.
It shows evidence of maritime trade and urban planning.
Step 2: Identify the discoverer.
The archaeological site of Lothal was discovered by S. R. Rao.
He was an important Indian archaeologist associated with the excavation of Lothal.
Step 3: Final conclusion.
Therefore, the correct answer is:
\[
\boxed{\text{S. R. Rao}}
\]