Leinster Women will play Harlequins at Twickenham three days after Christmas as part of a festive double-header.
The current inter-pro champions will face Quins, who currently lead the women's Premiership, in a friendly at RFU headquarters on 28 December.
The game will be played after the Gallagher Premiership fixture between Harlequins and Leicester Tigers.
Leinster wrapped up the 2019 inter-provincial championship title in September, having maintained an 100% record throughout.
Harlequins, meanwhile, are a nose ahead of Saracens at the summit of the Women's Premier 15s Table. They boast Irish internationals Anna Caplice and Leah Lyons within their ranks.
Leinster Women's head coach Ben Armstrong hailed it as "a hugely unique and historic event for girls and women's rugby in Leinster" and captain Sene Naoupu said she was "excited for the province, for rugby in Ireland and also for Harlequins, as a former player there myself".