Infrastructure as a Service (IaaS) is a cloud computing model in which a provider delivers virtualized computing resources, including servers, storage, networking, and operating systems, over the internet on a pay-as-you-go basis. Rather than purchasing and maintaining physical hardware in on-premises data centers, organizations rent these building blocks from IaaS providers and manage them through web consoles, APIs, or infrastructure-as-code tools.
The leading IaaS providers (Amazon Web Services, Microsoft Azure, and Google Cloud Platform) offer a broad spectrum of compute options ranging from virtual machines and bare-metal servers to GPU instances for machine learning workloads. IaaS also encompasses supporting services such as virtual private networks, load balancers, firewalls, and block or object storage. Users retain full control over the operating system, middleware, and applications running on the provisioned infrastructure.
IaaS sits at the base of the cloud service stack, below Platform as a Service (PaaS) and Software as a Service (SaaS), offering the greatest flexibility but also the most operational responsibility. It's a good fit for organizations that need granular control over their environments, want to run legacy applications in the cloud, or require custom configurations that higher-level abstractions can't accommodate. The elastic nature of IaaS lets teams scale resources up or down in minutes, turning capital expenditures into predictable operational costs.