Tehelka (transl. Sensation) is an Indian news magazine known for its investigative journalism and sting operations. According to the British newspaper The Independent, the Tehelka was founded by Tarun Tejpal, Aniruddha Bahal and another colleague who worked together at the Outlook magazine after "an investor with deep pockets" agreed to underwrite their startup. Bahal left Tehelka in 2005 to start Cobrapost – an Indian news website, after which Tehelka was managed by Tejpal through 2013. In 2013, Tejpal stepped aside from Tehelka after being accused of sexual assault by his employee. Tehelka had cumulative losses of ₹66 crore (US$7.8 million) till 2013, while being majority owned and financed by Kanwar Deep Singh – an industrialist, a politician and a member of Indian parliament (Rajya Sabha).

The magazine began circulating tabloid-format newspapers in 2004 and switched to magazine in 2007. Tehelka's first sting operation was on a cricket match fixing scandal in 2000. In 2001, it won national fame and public support for its sting "Operation West End". This 2001 undercover operation recorded and released footage of government officials accepting prostitutes and bribes in a fake arms deal. This caused the resignations of several officials including the then Defence Minister and two presidents of the ruling parties. In 2007, Tehelka published a report against members of the Bajrang Dal and for their role in the Naroda Patiya massacre during the 2002 Gujarat violence. The report, called "The Truth: Gujarat 2002", was based on a six-month sting operation with video footage of the members admitting their role in the violence. It won the International Press Institute (IPI) India Award for Excellence in Journalism in 2010 and 2011.

Tarun Tejpal, Aniruddha Bahal and a colleague quit their jobs from Outlook magazine and started Tehelka in New Delhi as a website in 2000.

Tehelka gained national fame when Aniruddha Bahal and Matthew Samuel completed and published undercover videotapes about corruption in a fake arms deal through the sting – "Operation West End" – in 2001. The Tehelka report triggered a government inquiry. The exposé caught senior defence personnel and politicians of the Samata Party, the Bharatiya Janata Party and others accepting bribes from a fake company offering fake defence products. The scandal and subsequent inquiry led to the resignation of many including India's Defence Minister. Politicians from various parties called for action against Tehelka journalists for its unethical methods such as procuring and providing prostitutes for its undercover sting. According to Navdip Dhariwal, the Tehelka staff saw the government inquiry as a direct attack on them. By 2003, Tehelka staff decreased from 120 to 3 and the website shut down because of debts. Bahal left Tehelka in the same year, saying the government was "bogging us down with a lot of legal nonsense" and later founded Cobrapost.com.

In 2004, after more than 200 writers, lawyers, business people and activists became founder-subscribers, Tehelka was relaunched as a reader-financed weekly newspaper in tabloid format. Among the supporters were activist Arundhati Roy, Congress party politician Shashi Tharoor and Nobel laureate V.S. Naipaul. It called itself the "People's Paper" and the reporters took a tour around the country promoting what they called "free, fair and fearless" journalism. After its Naroda Patiya sting operation in 2007, it sold around 75,000 to 90,000 copies per week. It still suffered large financial losses, since it attracted very few advertisements and the magazine primarily relied on subscribers and copies sold as of 2008. Tehelka had cumulative losses of ₹66 crore (US$7.8 million) through 2013, while being majority owned and financed by Kanwar Deep Singh – an industrialist, a politician and a member of Indian parliament (Rajya Sabha) initially elected by Jharkhand Mukti Morcha, later All India Trinamool Congress.

Tejpal changed Tehelka from tabloid to magazine in September 2007 to encourage more potential advertisers, but found it difficult because of their sting operations. Tejpal started the Hindi language website in 2007 and then Tehelka's Hindi News magazine. Sanjay Dubey was the executive editor of the Hindi magazine. In the early years, Tarun Tejpal was Tehelka's largest shareholder through his shell company Agni Media. In an interview to The New York Times, Tejpal stated that he covered the losses at Tehelka by soliciting funds from his personal contacts.

"THiNK Fest" was started in 2011 as an annual literary festival and promoted as an event of Tehelka, though the program was run by an organisation called Thinkworks Pvt Ltd, a company owned by Tejpal, his sister Neena and managing editor Shoma Chaudhury. It featured Bollywood actors, global thinkers and sessions on new technology.

According to The New York Times, during a Tehelka organized "Think Fest" event in November 2013, a staff reporter of Tehelka accused Tejpal of rape and repeated sexual assault. Tejpal was arrested by Goa police and he stepped aside as editor of Tehelka, and his colleague Shoma Chaudhury resigned from Tehelka on 28 November because of the incident. In 2014, Mathew Samuel became the managing editor of Tehelka. In March 2016, Charanjit Ahuja became the editor of the fortnightly.