<PAGE>
Filed Pursuant to Rule 424(b)(3)
Registration No.: 333-86257
Supplement, Dated November 16 , 1999, to Prospectus, Dated September 17, 1999,
- -------------------------------------------------------------------------------
of UnitedGlobalCom, Inc.
- ------------------------
Additional Selling Securityholders. The following selling securityholders are
added to the list of selling securityholders in the prospectus:
Number of Depositary Shares
---------------------------
Name of Selling Securityholder Owned Offered
- ------------------------------ ----------- -------------
IIU Convertible Fund Plc............................ 10,000 10,000
Paloma Strategic Securities Limited................. 75,000 75,000
