Rajendra Singh (born 6 August 1959) is an Indian water conservationist and environmentalist from Alwar district, Rajasthan in India.

The NGO based in village hori-Bhikampura in Thanagazi tehsil, near Sariska Tiger Reserve, has been instrumental in fighting the slow bureaucracy, mining lobby and has helped villagers take charge of water management in their semi-arid area as it lies close to Thar Desert, through the use of johad, rainwater storage tanks, check dams and other time-tested as well as path-breaking techniques.

[5] An important event in his life came in 1974, when he was still in high school, Ramesh Sharma, a member of Gandhi Peace Foundation visited their family home in Meerut, this opened up young Rajendra's mind, to issues of village improvement, as Sharma went about cleaning the village, opened a vachnalaya (library) and even got involved in settling local conflicts; soon he involved Rajendra in an alcoholism eradication program.

[5] Another important influence was an English language teacher in school, Pratap Singh, who started discussing politics and social issues with his students after class.

[5] Meanwhile, he joined Tarun Bharat Sangha (Young India Association) or TBS, an organization formed by officer and students of Jaipur University to aid victims of a campus fire.

However back at work, he was feeling increasingly frustrated by the apathy of his superiors towards developmental issues and his own inability to have a larger impact, he left his job in 1984.

[5] Alwar district, which once had a grain market, was at the time largely dry and barren, as years of deforestation and mining had led to a dwindling water table, minimal[clarification needed] rainfall followed by floods.

Another reason was the slow abandoning of traditional water conservation techniques, like building check dams, or johad, instead villagers started relying on "modern" bore wells, which simply sucked the groundwater up.

At this point he met a village elder, Mangu Lal Meena, who argued "water was a bigger issue to address in rural Rajasthan than education".

Though Rajendra wanted to learn the traditional techniques from local farmers about water conservation, his other city friends were reluctant to work manually and parted ways.

[9] In 2009, he led a pada yatra (walkathon), a march of a group of environmentalists and NGOs, through Mumbai city along the endangered Mithi river.