The 1998–99 Scottish Inter-District Championship was a rugby union competition for Scotland's professional district teams.

With the merging of the 4 districts into 2; now only Glasgow and Edinburgh were involved in the Scottish Inter-District Championship.

Glasgow Caledonians and Edinburgh Reivers then fought it out in a renamed Tri-Series sponsored by Tennents Velvet.

Edinburgh won the series, beating Glasgow 2-1.

Both teams entered the next year's Heineken Cup.