Semyon Pegov was born in Smolensk into a family of teachers. He studied at school according to the Waldorf system. He graduated from the Faculty of Philology of Smolensk State University, specialising in journalism. He was fond of rock climbing and tourism. Studied in the literary studio "Persona". Participated in the forum of young writers "Lipki-2011". Published poems in the Russian anthologies "Under the Clock", "Persona" and "Sovremenniki".

From 2006 to 2008 worked at the TV channel VGTRK "Smolensk". From 2007 to 2009 he was editor of BIGmag magazine. From 2008 to 2013 he worked at the Abkhaz TV channel Abaza TV. He wrote for the publications Nuzhnaya Gazeta, Chegemskaya Pravda and Novy Den. In 2014, he moved to LifeNews, where he gained fame as a war correspondent. Since 2017, he has been running the Telegram channel WarGonzo. As of November 2022, the channel has 1.3 million subscribers. Since the beginning of Russia's invasion of Ukraine, he has been covering the fighting in Ukraine. Since May 2022, WarGonzo has been removed from YouTube by the video hosting administration.

Author of the film "His Oplot", dedicated to the memory of the first head of the DNR Alexander Zakharchenko, the film "Callsign 'Donetsk': The Story of One Airport" about the storming of the Sergei Prokofiev Airport in Donetsk. In 2016, Pegov's book "Me and the red-haired separ" about business trips to Donbass, Crimea and Syria was published.

In October 2022, Pegov came under fire near the village of Vodyanoye in Donetsk region and suffered an open fracture of two toes of his right foot.

He has covered military conflicts in Georgia, Egypt, Syria, Nagorno-Karabakh and Ukraine. He is included in the database of the Ukrainian website "Peacemaker". On 15 January 2023, sanctions were imposed against Pegov by decree of the President of Ukraine. On 3 February 2023, the Prosecutor General's Office of Ukraine declared suspicion in absentia against Pegov for justifying Russia's war against Ukraine.