AWS Landingzone
A landing zone is a well-architected, multi-account AWS environment that is a starting point from which you can deploy workloads and applications. It provides a baseline to get started with multi-account architecture, identity and access management, governance, data security, network design, and logging.
Documentation

Azure CAF Enterprise Scale
Azure landing zone is an environment that follows key design principles across eight design areas. These design principles accommodate all application portfolios and enable application migration, modernization, and innovation at scale.
DocumentationGoogle Cloud Landingzone
Landing zones help your enterprise deploy, use, and scale Google Cloud services more securely. Landing zones are dynamic and grow as your enterprise adopts more cloud-based workloads over time.
Documentation