Software as a Service (SaaS) Definition Software as a service (SaaS) is a software distribution model in which a third-party provider hosts applications and makes them available to customers over the Internet. SaaS is one of three main categories of cloud computing, alongside infrastructure as a service (IaaS) and platform as a service (PaaS). SaaS removes the need for organizations to install and run applications on their own computers or in their own data centers. This eliminates the e...