Dolors Sala Carrio was 82.
"Everyone associated with the club sends their most heartfelt sympathy at this most distressing time to Pep, his family and all their friends," Manchester City said.
Guardiola donated €1 million to the Medical College of Barcelona in March to aid in the country's relief effort.
He also posted a video message instructing City supporters to remain at home to limit the spread of COVID-19:
Manchester City @ManCity
"WE'LL COME BACK FROM THIS STRONGER..." 💪 #CityzensAtHome is here to bring you regularly updated news, advice and a wide range of fun and educational activities, centred on football, for the whole family to enjoy in your homes. https://t.co/twd82HAhpP https://t.co/xrOwQzVSua
According to CNN, the World Health Organization has confirmed nearly 1.3 million cases of coronavirus across the world amid the COVID-19 pandemic. Spain has the second-highest number of cases (135,032) and deaths (13,055).