Having won her first-ever top-level final, 22-year-old Navarro will enter her debut Australian Open seeded 27th and on a high after upsetting top seed Mertens 6-1 4-6 7-5 in two hours, 48 minutes at the Domain Tennis Centre.
"I don't know if I can put words to the emotion but it's been a lot of years in the making," Navarro said.
"I played a really good first set, then I let the nerves get the best of me a bit in the second set.
"Holding serve was really tough with the wind.
"(I'm) really happy that I was able to stick in there physically and mentally.
"To be here now is really crazy."
Second-seed Navarro thumped 39 winners to Mertens' 24 on Saturday, strong-arming the more experienced Belgian from the baseline and regularly climbing into her serve to register eight breaks.
The American barely put a foot wrong to take the lopsided opening frame in 35 minutes before moving a break up in the second set.
Mertens, troubled all afternoon by the blustery conditions, dug deep to save six break points to hold from 0-40 down in the ninth game of the second set before breaking to level the match.
The Belgian, who ended hometown hope Daria Saville's ambitions with a narrow semi-final victory on Friday, broke Navarro in five successive games and, despite being below her best, looked like her big-match know-how may get her home.
But Navarro continued her unrelenting attack, breaking Mertens to 15 with a sublime off-forehand, then sealing the biggest win of her career in the next game with another forehand winner.
"That's the game of tennis - sometimes you win, sometimes you lose," Mertens said.
"I gave everything I had today. She played well in the key moments.
"All credit to her for not getting nervous at the end for her first title."
