In an announcement that will remind viewers of the 2020 and 2021 series which saw various contestants ruled out with the virus, BBC One confirmed that Marsh and her partner Graziano Di Prima would be unable to dance in Saturday's live show.
A spokesperson said: "Kym Marsh has tested positive for COVID-19. As a result, Kym and Graziano will not be taking part in Strictly Come Dancing this weekend. Strictly Come Dancing protocols mean that all being well, they will return the following week.”
This is the first time in the 2022 series that a couple has been unable to compete over a positive COVID result.
In the 2020 series, Nicola Adams and her partner Katya Jones had to quit the competition after week three with positive COVID results because of strict isolation protocols.
Read more: Why is Blackpool so important to Strictly?
Last year, Di Prima was forced to take a week off for the same reason when his partner Judi Love tested positive for COVID, and Tom Fletcher and Amy Dowden also had a week off with COVID.
Other Strictly COVID-related absences in previous series have included judges Craig Revel Horwood who tested positive, Motsi Mabuse who had to isolate after travelling to Germany, and Bruno Tonioli who was unable to travel between the US and UK in the 2020 and 2021 seasons.
Former footballer Tony Adams quit the contest recently due to injury, announcing moments before the dance off that he would be unable to take part.
Marsh and Di Prima are expected back on the dancefloor next weekend for the quarter-finals.
Last weekend, Strictly travelled back to Blackpool's Tower Ballroom for the first visit since 2019, with COVID restrictions having kept the show away in the last two series.
The show saw Fleur East and Vito Coppola achieve the first perfect 40 for their couple's choice routine, while Tyler West and Dianne Buswell were voted out.
Strictly Come Dancing continues on Saturday at 7.15pm on BBC One.
Watch: Who is Strictly's Kym Marsh?