The 1998 Regional Council by-election was held on 29 October 1998 after the court ruled the incumbent Legislative Councillor Tang Siu-tong was unduly elected in the Regional Council constituency due to invalid ballots.

[1] Tang eventually recaptured his seat with a larger margin in this by-election.

Preferential elimination system of voting was in place for the election of the Regional Council constituency.

In the Regional Council constituency, Tang Siu-tong defeated Ann Chiang in the second round with a 25–24 margin.

[4] Ngan Kam-chuen was eliminated again in the first round, and Tang won the seat with a widened margin.