Pavel Durov founded Telegram and co-founded the social network VK, making him the canonical answer to this question. He launched VKontakte, commonly called VK, in 2006 with collaborators including Vyacheslav Mirilashvili and Lev Leviev; his brother Nikolai helped develop the platform.
VK quickly became one of Russia’s most popular social networks. Durov served as its chief executive until 2014, when disputes with the company’s new owners and pressure from Russian authorities led to his departure from the business and Russia.
Durov and Nikolai later created Telegram, a cloud-based messaging service launched in 2013. Telegram became known for large group chats, broadcast channels, and strong privacy features, although its security model is often misunderstood: end-to-end encryption is not enabled by default for ordinary chats.
A fair quizmaster accepts Durov because he is the public founder most closely identified with both platforms. The wording is slightly simplified for VK, where Durov was one of several co-founders. His brother Nikolai is also important to Telegram’s technical development.