Following the conclusion of the Challenge Cup pool stages on Saturday, Chris Boyd's side, who dropped into the competition from the Champions Cup, found out their fate.
And it will be a trip to Kingsholm to take on a Cherry and Whites team who are current rivals for Saints in the pursuit of a play-off place in the Gallagher Premiership.
Saints lost 35-30 at Gloucester in the league last month, but if they are able to win their last-16 tie they would travel to the winner of the game between Saracens and Cardiff Blues.
The ranking of the clubs for the Round of 16 was as follows...
(i) the three EPCR Challenge Cup pool winners are ranked 1st to 3rd
(ii) the three EPCR Challenge Cup pool runners-up are ranked 4th to 6th
(iii) the three EPCR Challenge Cup third-placed clubs are ranked 7th to 9th
(iv) the leading fourth-placed EPCR Challenge Cup club is ranked 10th
(v) the six Heineken Champions Cup qualifiers are ranked 11th to 16th
And that means the draw looks as follows...
Friday (April 15)
London Irish v Castres Olympique, Brentford Community Stadium (17.30)
Biarritz Olympique v Wasps, Parc des Sports Aguiléra (18.30)
Newcastle Falcons v Glasgow Warriors, Kingston Park (20.00)
Lyon v Worcester Warriors, Matmut Stadium de Gerland (21.00)
Saturday (April 16)
Edinburgh Rugby v Bath Rugby, DAM Health Stadium (20.00)
Gloucester Rugby v Northampton Saints, Kingsholm (20.00)
RC Toulon v Benetton Rugby, Stade Félix Mayol (21.00)
France 4 / beIN SPORTS
Sunday (April 17)
Saracens v Cardiff Rugby, StoneX Stadium (13.00)
BT Sport / S4C
Quarter-finals - May 6/7/8
Clubs with the higher rankings will have home venue advantage in the quarter-final matches as follows...
QF 1: winner Match 1 v winner Match 8
QF 2: winner Match 3 v winner Match 6
QF 3: winner Match 2 v winner Match 7
QF 4: winner Match 4 v winner Match 5
Semi-finals - May 13/14/15
Clubs with the higher rankings will have home venue advantage in the semi-final matches as follows...
SF 1: winner QF 1 v winner QF 2
SF 2: winner QF 3 v winner QF 4
2022 EPCR Challenge Cup final: Friday, May 27: Stade Vélodrome, Marseille (9pm)