Emma McCreadie stumbled across the animal in July last year on a footpath near her home in Twechar.
She said: “I was walking with my daughter, mum and dog and there it was – only about 20 feet away from us.
“It was about the size of a large dog – black, slender, with a really long tail, pointy ears and greeny-yellow eyes.
“I looked at it for about 20 seconds then panicked, got my daughter and walked away.
“The dog didn’t seem to pay it any attention at all.”
A couple of weeks later one of Emma’s neighbours also saw the creature, which prompted her to find out more.
She said: “I wasn’t going to report it because I thought people would think I was crazy.
“I ‘googled’ it and found the Big Cats in Britain website, learned about lots of other sightings and told them about it.
“They got in touch with me and asked if I’d deal with any big cat encounters around Glasgow.”
Now Emma wants to hear reports from anybody who has had a similarly unusual sighting.
She said: “I go up into the hills with my boyfriend regularly and am always looking out for big cats.
“I’d love to see another one. They don’t scare me as there’s never been any report of them attacking humans. They just seem to want to be left alone.
“The ultimate aim would be to get firm evidence of a big cat living near Glasgow.”
If you have seen a big cat you can contact Emma by e-mailing [email protected]
For more information about sightings go to www.bigcatsinbritain.org