The best open source alternative to Pulumi is OpenTofu. If that doesn't suit you, we've compiled a ranked list of other open source Pulumi alternatives to help you find a suitable replacement.
Pulumi alternatives are mainly Infrastructure as Code (IaC) Tools. Browse these if you want a narrower list of alternatives or looking for a specific functionality of Pulumi.
A community-driven, truly open-source fork of Terraform for managing cloud infrastructure through code.

OpenTofu is an open-source infrastructure as code tool, forked from Terraform in response to HashiCorp's license change. It aims to provide a truly open, community-driven alternative for managing cloud resources through code.
Key features and benefits:
Truly open-source: Licensed under a well-known, widely-accepted open-source license, ensuring long-term stability and trust for companies.
Community-driven: Governed by the community for the community, with regular review and acceptance of pull requests based on merit.
Impartial: Features and fixes are accepted based on their value to the community, not influenced by any particular vendor.
Layered and modular: Designed with a programmer-friendly structure to encourage building on top and fostering a vibrant ecosystem of tools and integrations.
Backwards-compatible: Ensures existing code remains valuable and functional for years to come.
Drop-in replacement: Compatible with Terraform versions 1.5.x and most of 1.6.x, allowing for seamless migration without code changes.
Production-ready: Suitable for production use cases without exceptions.
Strong support: Backed by major companies like Harness, Gruntwork, Spacelift, env0, and Scalr, ensuring long-term development and maintenance.
Community-focused development: Encourages contributions and actively listens to community issues and feature requests.
Future-proof: Aims to maintain feature parity with Terraform while allowing for community-driven innovations and improvements.
For organizations and individuals looking for a stable, open-source solution for infrastructure as code, OpenTofu provides a compelling alternative to Terraform, ensuring continued access to powerful IaC capabilities without licensing concerns.