Step 1: Understanding the Concept:
The question asks to identify the social reform organization founded by the 19th-century social reformer, Jyotirao Phule (also known as Jyotiba Phule).
Step 2: Detailed Explanation:
- Jyotirao Phule founded the Satya Shodhak Samaj (Truth-Seekers' Society) in Pune, Maharashtra, on 24 September 1873.
- The main objective of the organization was to liberate the Shudra and Ati-Shudra (Dalit) castes from exploitation and oppression by the Brahmin caste. It advocated for social equality, education, and justice for the lower castes.
- The Harijan Sevak Sangh (D) was founded by Mahatma Gandhi in 1932.
Step 3: Final Answer:
Jyotirao Phule established the Satya Shodhak Samaj.