Rhinos - beaten 28-0 by Saints in last year's Grand Final - became the first team to score against them this season and led from the 15th to the 48th minute, but the defending champions proved stronger in the final quarter.
Though Saints were deserved winners, scoring four tries to one, Rhinos pushed them much closer than the final score suggests.
They rocked Saints at times with their powerful defence, failure to make more of their chances proved costly.
Prop Zoe Hornby scored an outstanding solo try to give Rhinos the lead, storming over from 30 metres out and beating Amy Hardcastle’s last-ditch tackle.
Courtney Winfield-Hill added the extras and Rhinos created a series of opportunities to go further in front, particularly when Danielle Anderson squeezed out an offload to Elychia Watson, but she spilled the ball just short of the line.
Saints struck back eight minutes before the break when Zoe Harris’ kick on the last found Leah Burke in space on the right wing, though she touched down too far out for Bethany Stott to convert.
Winfield-Hill landed a penalty goal with the final kick of the first half, following a high tackle by Chantelle Crowl on Emma Lumley and the captain’s pass was close to creating a try for Watson early in the second period, but Rebecca Rotheram made a try-saving tackle.
Saints levelled with a scrappy touchdown on 48 minutes. Stott’s kick was fumbled on Rhinos’ line by Tasha Gaines, Chloe Kerrigan and Keara Bennett couldn’t pick up and Eboni Partington fell on the ball to score, though the conversion attempt was missed.
The pivotal moment of the final came with 18 minutes left. Fran Goldthorp almost scored with a brilliant solo run and then Winfield-Hill was off-target with a penalty attempt for an obstruction in back play.
From the tap, Saints surged upfield and Woman of Steel Jodie Cunningham burst through a tiring defence and score a try which Stott improved .
The official attendance of 5,888 was a record for a women's game in this country.