Mia Livesey, eight and from Wednesbury, has raised enough money to help two other girls get wigs who have sadly lost their hair through illness.
The money will go to The Little Princess Trust.
The Mesty Croft Academy pupil decided to carry out the brave initiative after learning of the charity's work from her mother, Kirsty Tubb, 29.
Mia's grandmother, Claire Mansell, 48, from Wednesbury, said the family were "really proud" of her act of kindness.
Ms Mansell said: "Mia wanted her hair cut anyway, but then she was talking with her mom about the Little Princess Trust and what they do.
"Her mom told her that they make wigs for children who have gone through cancer treatment or other illnesses causing them to lose their hair.
"When she found out, Mia said she definitely wanted to help out.
"We are really proud of her. This is something that she wanted to do herself. It costs at least £550 to make one wig.
"The money will help two little girls get wigs."
Mia set an original fundraising target of £300 but her campaign has now raised more than £1,000 – and counting.
The haircut was done by Faye Lawley at the Tangled Salon, in West Bromwich, where she cut off 12 inches.
Ms Mansell added: "Everybody have been so generous. We are just absolutely shocked at the amount, considering everybody is going through hard times and people are losing their jobs."
To donate to Mia's fundraising campaign, visit www.justgiving.com/mias-haircut