She was among a group of six climbing in pairs near the Pigme Ridge on Coire an t-Sneachda in the Cairngorms yesterday.
As she and her climbing partner made the ascent she was struck by a falling boulder.
He carried out CPR but she could not be resuscitated.
The other four who had finished the route raised the alarm and Cairngorm Mountain Rescue Team (CMRT) and the Royal Navy Sea King Helicopter Rescue 177 went to the scene when the alarm was raised at about 2.30pm.
Willie Anderson, Team Leader of CMRT, said: "They were climbing the route in three sets of two and as the last two went up quite a large stone boulder fell and hit the lady on the head.
"No-one dislodged it but there has been so much rain that lots of rocks are loose at the moment."
The group of six met through an online climbing forum. It is thought the woman was in her mid fifties.
A report will be submitted to the procurator fiscal. The victim's name will not be released until next of kin are informed.
Coire an t-Sneachda is described in online guides as one of Britain's high mountain corries, with an easily accessible path. One website described the corrie itself as "a grand cirque of cliffs," but added that climbers need to be very careful as its floor is more than 900 metres high.
Many climbers have been taking to the hills due to the good weather, with sunshine and good visibility from the summits.