The pensioner was walking with a group of 11 people along a trail above the village of Saas-Almagell when for a reason not immediately known she fell 100 metres down a steep slope, Valais cantonal police said.
The incident occurred at around 1.30pm, police said.
The hikers were heading to the top of the Heidbodme chairlift, at an altitude of 2,400 metres, more than 1,300 metres above the village.
An emergency rescue team from Air Zermatt responded to an emergency call but the woman was dead by the time they arrived, police said.
The death followed two other fatalities involving hikers in the Valais mountains last week.
Another retiree, a 76-year-old Swiss man from the canton of Zug, died after falling from a trail down a deep slope into the Merezenbach stream, according to the initial evidence, police said.
The man had been hiking on Wednesday from the village of Reckingen in the Upper Rhone Valley, which he left at 6am, and was heading to Geschinen, (another village in the valley) via a mountain trail.
Around 7pm he phoned his wife to say that he had just an hour to go before he arrived in Geschinen, police said.
A search involving an Air Zermatt helicopter was launched when he failed to turn up.
With light failing, the search was resumed the following day when rescue workers found the man's body.
Elsewhere, the lifeless body of a 53-year-old German man was discovered between the Otanes Pass (at an altitude of 2,846 metres) and Le Grand Tavé mountain (3,158 metres) in the Bagnes valley last Wednesday, cantonal police said.
The man, who was identified a day later, appeared to have fallen 100 metres into a pile of rocks from a mountain trail.