Despite the Blues having Australian bowler Megan Schutt (2/15) back in the side for the second time this season, it was player of the match Stacey Oates (4/37) who made the most impact in the attack.
Oates took her second consecutive four-wicket haul, bringing her total scalps to 22 for the season, while Sarah Carver collected her best bowling figures for the year of 3/5.
Southern District were looking comfortable at 0/30 before captain Jess O’Reilly became Oates’ first victim.
Donna Clark (25) held on as long as she could but the loss of her wicket, as well as Kelly Armstrong (1) and coach Hannah Sampson (0) cheaply put pressure on the middle and lower order.
Selina Solman (15) and Rachel Andrew (12) dug in for a 32-run partnership and Ella Wilson (15) contributed valuable lower-order runs, but the Stingrays were dismissed for 104 in the 43rd over.
Annie O’Neil (29) and Eliza Bartlett started the Blues’ chase well, before Solman struck to remove the latter for nine.
Once O’Neil and Emma de Broughe (14) were dismissed, Alex Price (26 not out) and Rhianna Peate (14 not out) combined for a 41-run partnership, clinching the title with more than 21 overs remaining.
Sturt last won the First Grade title in 2010-11 against Port Adelaide.