The 57-year-old singer has shared some images of a trip to Kibra, also known as Kibera, with Shining Hope for Communities, a charitable organisation which links free schools for girls to services for communities such as clean water and free health care, reported Female First.
Alongside one picture of young children she simply wrote: "Striking a Pose in Kibera! Rebel Hearts."
Madonna also posted a picture of a litter-strewn river and wrote, "Imagine this is where your water comes from! @shofco is working to change this in Kibera, Africa's largest slum.