The Norwegian curled home a long-range strike just after the hour mark to settle a tight contest at Meadow Park. Arsenal had been frustrated for large parts of the game, after Katie McCabe had a penalty saved in the seventh minute.
But they got the win and it was one that lifted Arsenal to within two points of third-placed Chelsea and three behind Manchester City in second, on whom they have a game in hand. The race for the title, and a top-three finish to secure Women’s Champions League football next season, looks set to go down to the wire.
Arsenal, looking to bounce back from their Champions League exit to Wolfsburg on Monday, started strongly and had a chance to take an early lead after McCabe was brought down in the area by Hannah Cain.
McCabe stepped up to take the resulting spot-kick but was denied by the excellent Janina Leitzig.
Leicester threatened through Cain but her shot was blocked by keeper Sabrina D’Angelo before Victoria Pelova spurned a chance for the hosts.
Cain was denied again by D’Angelo in the 62nd minute and was left to rue the opportunity as Maanum found the top corner from the edge of the area following a Jodie Taylor cut-back.
Arsenal finished strongly with Taylor hitting the side-netting and Maanum twice forcing Leitzig to save, before hitting the bar from a free-kick, and the Gunners did enough to see out the match through ten minutes of stoppage-time.
Additional reporting by PA Sport.
