The Satyashodhak Samaj (Truth-Seeking Society) was founded by Mahatma Jyotiba Phule in 1873. This organization played a significant role in advocating for social reform and equality, particularly for the lower castes and women in India. Phule's mission was to challenge the caste system and promote education, especially for marginalized communities.
Here's why the other options are incorrect:
- Option (1): Rajaram Mohan Roy: Rajaram Mohan Roy was a prominent social reformer who founded the Brahmo Samaj in 1828. While he worked for social reforms, including the abolition of sati and child marriage, he did not found the Satyashodhak Samaj.
- Option (2): Ishwar Chandra Vidyasagar: Ishwar Chandra Vidyasagar was a renowned scholar and social reformer who worked extensively for women's rights and education. However, he did not establish the Satyashodhak Samaj.
- Option (3): Mahatma Jyotiba Phule: This is the correct answer, as Mahatma Jyotiba Phule founded the Satyashodhak Samaj to fight against social inequalities, particularly the caste system. He also authored influential works like *Gulamgiri* ("Slavery") to advocate for social justice.
- Option (4): Gopal Krishna Gokhale: Gopal Krishna Gokhale was a key leader of the Indian National Congress and a social reformer who focused on political and educational reforms. However, he did not establish the Satyashodhak Samaj.
Answer: $\boxed{\text{Mahatma Jyotiba Phule}}$