Voters are going to the polls in the Rutherglen and Hamilton West by-election.
The seat was vacated after former SNP MP Margaret Ferrier was ousted in a recall petition.
Ms Ferrier was kicked out of the SNP for breaching Covid regulations by travelling between London and Glasgow after testing positive for the virus.
SNP candidate Katy Loudon goes up against Labour’s Michael Shanks and Tory hopeful Thomas Kerr in the by-election on Thursday.
Cameron Eadie and Gloria Adebo are running for the Greens and Scottish Liberal Democrats, respectively.
Other candidates running are:
The election will be the first in Scotland to require voters to show photo ID before they are allowed to cast their ballot following a change in Westminster legislation that governs Westminster elections.
Counting will be conducted at the headquarters of South Lanarkshire Council in Hamilton, with a result expected in the early hours of Friday.
Polling stations opened at 7am on Thursday and close at 10pm.