Martinez Sanchez stroked nine aces in defeating the Austrian wild card 6-0, 7-5, collecting her fourth career WTA singles title and the first since last year's event in Rome.
The 28-year-old Spaniard was appearing in her fifth career final, all of which have come on clay surfaces.
Mayr-Achleitner, 24, meanwhile, was making her first trip to a WTA final.
She had reached the championship match by dispatching Russian Ksenia Pervak, 6-0, 6-0 Saturday. Her one-sided win was the first "double bagel" in a WTA semifinal since 2005.
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