The Dunedin athlete soared 5.74m with the opening jump of the competition, adding 3cm to the T47 long jump Paralympic Games record in Tokyo.
It was a distance only she surpassed.
Her fourth jump of 5.76m was the final winning distance as she defended the gold medal she won in Rio five years ago.
Russian Olympic Committee jumper Aleksandra Moguchaia and Ecuador's Kiara Rodriguez pulled out jumps of 5.67m and 5.63m to win the other medals.
While she later said she had been so nervous during the competition she felt she might vomit, Grimaldi was in complete control.
Her three legal attempts were all among the top four jumps of the competition.
It was a contrast from Rio, when she pulled off a mammoth 21cm personal best with her final jump of 5.62m to snatch a shock gold medal.
That was not lost on Grimaldi, who said she was ‘‘in a whirlwind'' following the event.
‘‘In Rio I won by accident, but here I did it on purpose,'' Grimaldi (24) said.
‘‘That's how I feel. There's been so much that's gone into this one.
‘‘I’ve changed as a person, and I hope it is obvious to people watching how different I am. I’m really proud.’’
The para-athlete’s mother, Di Grimaldi, watched coverage with her husband and Anna’s younger sister Abby (18) in Dunedin.
The family were relieved when she nailed her first jump and her mother said she had looked comfortable before it.
‘‘She looked really happy and excited to be there.’’
Her father, Tony Grimaldi, said he was extremely nervous as he followed her progress.
The family jumped, screamed and hugged when the win was confirmed, he said.
‘‘We’re so pleased for her.’’
The win followed a challenging five years for Grimaldi, who was sidelined for 18 months with a stress fracture in her foot in 2017 and 2018.
There were times she had been unsure she would make it to Tokyo.
But she stuck at it with coach Brent Ward and her support team, eventually surpassing her personal best from Rio last summer.
‘‘It has been a huge five years and I just feel the weight of the world has lifted off my shoulders,'' she said.
Grimaldi is due to fly home today and go into quarantine.
Fellow Dunedin Paralympian Holly Robinson competed in the F46 javelin late last night.
- Additional reporting by Grant Miller
