The 1998–99 National League 1, sponsored by Jewson, was the twelfth full season of rugby union within the third tier of the English league system.

Two teams were relegated to either National League 2 North or South, depending on geographical location.

[1][2] Ten of the clubs participating in last seasons competition.

To make up the numbers two of the teams (Birmingham & Solihull and Manchester) were promoted from National 2 North, and two from National 2 South (Camberley and Henley) were also promoted.

National League 1 is sponsored by the building suppliers, Jewson.