| Season: | 1998–99 |
| Competition: | Omani League |
| Winners: | Dhofar |
| Relegated: | Oman Al-Ittihad |
| Matches: | 90 |
| Total Goals: | 224 |
| Prevseason: | 1997–98 |
| Nextseason: | 1999–2000 |
The 1998–99 Omani League was the 23rd edition of the top football league in Oman. Al-Nasr S.C.S.C. were the defending champions, having won the 1997–98 Omani League season. Dhofar S.C.S.C. emerged as the champions of the 1998–99 Omani League with a total of 34 points.
This season the league had 10 teams. Quriyat Club and Buraimi SC were relegated to the Second Division League after finishing in the relegation zone in the 1997–98 season. The two relegated teams were replaced by Second Division League teams Al-Suwaiq Club and Fanja SC.
| Club | Home city | Stadium | Capacity |
|---|---|---|---|
| Al-Ittihad | Salalah | Al-Saada Stadium / Salalah Sports Complex | 12,000 / 8,000 |
| Al-Nasr | Salalah | Al-Saada Stadium / Salalah Sports Complex | 12,000 / 8,000 |
| Al-Oruba | Sur | Sur Sports Complex | 8,000 |
| Al-Seeb | Seeb | Seeb Stadium | 14,000 |
| Al-Suwaiq | Al-Suwaiq | Sohar Regional Sports Complex | 19,000 |
| Dhofar | Salalah | Al-Saada Stadium / Salalah Sports Complex | 12,000 / 8,000 |
| Fanja | Fanja | Seeb Stadium | 14,000 |
| Oman | Muscat | Sultan Qaboos Sports Complex / Royal Oman Police Stadium | 39,000 / 18,000 |
| Sohar | Sohar | Sohar Regional Sports Complex | 19,000 |
| Sur | Sur | Sur Sports Complex | 8,000 |