Littler had navigated a challenging route to the finale, beating Jeffrey de Graaf, Ross Smith, Ricardo Pietreczko and Chris Dobey before overcoming Gerwyn Price 11-8 in the semi-finals.
Aspinall, ranked 21 in the world, entered the showdown in a confident mood after easing past Jermaine Wattimena 11-2, but was ultimately unable to derail the teenage darting prodigy.
Littler raced into a 5-2 lead, only for the Asp to fight back with a spirited run, highlighted by a 127 checkout that reduced the deficit to 9-8.
The 18-year-old, however, held his nerve to seal the title with an assured 88 finish.
"It wasn’t easy to reach the final, but I’m proud to tick this one off the list... only two more to go," Littler said after his latest triumph.
"I played brilliantly throughout, and I’m glad I got the job done as we look ahead to the big one next month."
More to follow...