| 1998 Croatia Open Umag | |
|---|---|
| Date | 27 July – 2 August |
| Edition | 9th |
| Category | World Series |
| Draw | 32S / 16D |
| Prize money | $375,000 |
| Surface | Clay / outdoor |
| Location | Umag, Croatia |
| Champions | |
| Singles | |
 Bohdan Ulihrach [1] | |
| Doubles | |
 Neil Broad /  Piet Norval [2] | |
The 1998 Croatia Open Umag was a men's tennis tournament played on outdoor clay courts in Umag, Croatia that was part of the World Series of the 1998 ATP Tour. It was the ninth edition of the tournament and was held from 27 July until 2 August 1998. Seventh-seeded Bohdan Ulihrach won the singles title.
