Amazon Web Services (AWS) allows firms to rent cloud servers in order to host data on the internet without needing to invest in their own infrastructure.
On Tuesday, sites such as Quora, a Q&A forum, and Trello, which helps people monitor productivity, went down.
After several hours, Amazon said it had rectified the problem.
It did not make public the reason behind the disruption.
As well as sites that went down, other services, such as workplace collaboration tool Slack, also lost some key functionality.