Alexander Mamut was born on 29 January 1960. His Father is Leonid Solomonovich Mamut, Doctor of Jurisprudence, Lawyer, one of the authors of the Russian Constitution, and his mother is Cicilia Ludwigovna, a defense attorney. In 1977 Mamut finished Moscow gymnasium #17, in 1982 graduated from Moscow State University, Faculty of Law.
In 1990 together with Andrey Gloriozonov, Mamut founded "Business and Cooperation” Bank, that was renamed in 1991 into Commercial Bank “Imperial”. The bank was founded to Service companies in the field of fuel and Energy. Its biggest clients were Gazprom and Lukoil. In 1990 Mamut founded “ALM-Consulting” law firm (ALM abbreviated after Mamut’s name) and served as Managing Partner there throughout 1990–1993. Mamut founded the Company of Project Financing in 1993, and served as its chief executive officer until 1998. Meanwhile, he was the co-founder and Director of Sedmoy Continent from 1993 to 1997. He was the founder of ALM Development and remained an investor until 2001.
Mamut served as the Chairman of Moscow Business World (MDM-Bank) from 1999 to 2002. He founded the SUP Company in 2006, and acquired LiveJournal Russia in 2007. That year, he also founded the “Most” Restaurant and Club. Mamut’s “A&NN” Investment Company acquired 100% of shares of Evroset from Evgeniy Chichvarkin and Timur Artemiev in 2008. By October 2008, he sold 49.9% to VimpelCom. Meanwhile, he acquired the “Pioneer” Movie Theatre and renovated it.
Mamut served as the Chairman of the Board of Trustees of Teatr Praktika, a theatre whose Director was Eduard Boyakov. By 2009, he served as the Chairman of the Board of Trustees of the Strelka Institute for Media, Architecture and Design. The Institute aims to change the landscape of Russian cities.
Mamut became the sole owner of the SUP Media in December 2012. By 2014, he became the Chairman of Rambler&Co. He is also the owner of Lenta.ru, a news website.
On the Forbes 2016 list of the world's billionaires, he was ranked #722 with a net worth of US$2.4 billion.