A-level student Victoria Rathmill from Macclesfield, Cheshire, signed up to the Anthony Nolan bone marrow register in February when she was 16. Just a few months later she was matched to a patient.
A spokeswoman from Anthony Nolan confirmed that Victoria was youngest ever person to provide stem cells to a non-relative.
Henny Braund, the organisation's chief executive said Victoria's 'historic donation is genuinely impressive'.
"It shows both what a special young woman she is, and how teenagers can be sufficiently mature, caring and engaged with the world around them to help save an unwell stranger," she said.
Speaking to ITV, Victoria said the donation process was 'just like giving blood' and revealed she had been motivated to join the register after a family friend was diagnosed with leukaemia.
"At first I was like: 'I'll join when I'm 18, I'm not going to make any difference', but then a friend of our family got ill and so I felt the need to join up," she said.
"It was only a couple of weeks after I signed up that I told my mum. Anthony Nolan sent the spit kit out to me and she asked me what it was. Though she was taken aback a bit at first, she thought it was a nice thing to do, especially given our friend's experience.
"After I signed up I just stopped thinking about it really. You just don't expect to get the phone call within six months of registering.
"It's quite shocking to think I'm the youngest-ever - you're never the first to do anything nowadays, it's all been done already."
Victoria's mum Paula told ITV of her pride in her 'headstrong' daughter: "Victoria's always been headstrong and determined but it never really occurred to me to try and stop her from helping another person in their hour of need. It makes me very proud."