The pair met in the ring as amateurs, with Briton Marshall outpointing her American rival, who is out for revenge in their rematch this weekend.
Shields, 27, carries the WBA, WBC, WBF and IBF middleweight titles into the O2 Arena, while Marshall, 31, puts the WBO belt on the line.
Each woman is unbeaten as a professional at 12-0, though Marshall has 10 knockouts compared to Shields’ two.
Here’s all you need to know as the old rivals headline an all-female card.
When is it?
Shields vs Marshall will take place at the O2 Arena in London on Saturday 10 September.
The first fight of the night will begin at 5pm BST (9am PST, 11am CST, 12pm EST), with the main card following at 8pm BST (12pm PST, 2pm CST, 3pm EST).
Ring walks for the main event between Shields and Marshall are expected to take place at 10pm (2pm PST, 4pm CST, 5pm EST).
How can I watch it?
The event will air live on Sky Sports Main Event and Sky Sports Arena in the UK, with coverage beginning at 7.30pm BST (11.30am PST, 1.30pm CST, 2.30pm EST). Sky subscribers can also stream the action live on the Sky Go app.
In the US, ESPN+ will air the bout live.
Marshall – 10/11
Draw – 14/1
Claressa Shields vs Savannah Marshall (undisputed women’s middleweight title)
Mikaela Mayer vs Alycia Baumgardner (unified women’s super-featherweight title)
Lauren Price vs Timea Belik (women’s welterweight)
Karris Artingstall vs Marina Sakharov (women’s featherweight)
Caroline Dubois vs Milena Koleva (women’s lightweight)
Ebonie Jones vs Vanessa Caballero (women’s super-bantamweight)
April Hunter vs Erica Alvarez (women’s super-welterweight)
Georgia O’Connor vs TBC (women’s super-welterweight)
Shannon Ryan vs Bucha El Quassi (women’s super-flyweight)
Ginny Fuchs vs Gemma Ruegg (women’s super-flyweight)
Sarah Liegmann vs Bec Connolly (women’s super-bantamweight)