The WTA Tier I tournaments were Women's Tennis Associationtennis elite tournaments held from 1990 until the end of the 2008 season. From 1988 to 1990, the different levels of WTA tournaments were referred to by the term 'Category', and there were 5 categories. Two of the Tier I tournaments, Indian Wells and Miami, were also joint events held simultaneously with the ATP TourMasters Series. There were initially 6 Tier I tournaments held annually from 1990. The list expanded to 8 events in 1993, 9 in 1997 and 10 in 2004, before being scaled back to 9 for 2008. In 2009 the WTA changed the tournament categories, so that the majority of Tier I and Tier II tournaments were in one category, Premier Tournaments, split into three categories.
DOH = Doha, IND = Indian Wells, MIA = Miami, CHA = Charleston, BER = Berlin, ROM = Rome, CAN = Canada, TOK = Tokyo, MOS = Moscow, SAN = San Diego, ZUR = Zürich, CHI = Chicago, BOC = Boca Raton, PHI = Philadelphia.
Miami before 2000 was held in Key-Biscayne, Charleston before 2001 was held in Hilton Head, Tokyo in 1993 was held in Yokohama; Chicago has been a Tier I only in 1990, Boca Raton in 1991 and 1992, Philadelphia from 1993 to 1995, Zürich from 1993 to 2007 and San Diego from 2004 to 2007.
; Winners of the series tournaments on three surfaces:
Navratilova.
A number of players hold records for winning the tournaments multiple times, while other records are achieved for successive tournament wins, mini-combination victories amongst others.
Conchita Martínez won the Italian Open four straight times, from 1993 to 1996, and reached the final in 1997.
Martina Hingis has won all the different Tier I tournaments except for the San Diego event, which became a Tier I event in 2004, during her three-year withdrawal from the sport which ended in late 2005.
