The fund will be invested in early stage, growth and late-stage businesses across North America, Europe and Asia.
Warburg Pincus currently has more than US$35bn of assets under management.
Fund X follows Kohlberg Kravis Roberts, which raised US$17.6bn at the end of 2007 and Advent International, which closed its US$10.4bn global fund at the beginning of April, shortly after Apax Partners closed an €11bn fund. Blackstone is understood to be marketing a new global fund of approximately US$20bn, CVC Capital Partners is also believed to be raising a new global fund.