The argument "region" is required, but was not set.

terraform apply or terrform validate
╷
│ Error: Missing required argument
│
│ The argument "region" is required, but was not set.
╵

Known bug, solution: export AWS_DEFAULT_REGION=us-east-1 

See also

• Terraform, OpenTofu, Installation, Terraform AWS, Terraform GCP, Terraform commands, Terraform Cloud, Terraform Enterprise (TFE), HCL, HIL, meta-arguments, providers, modules, resource, provisioners, data sources, backends: remote backends, examples, configuration files, state files, variables, types, Terraform Registry, conditionals: depends_on, functions, Blocks, dynamic blocks, errors, Terragrunt, Terraformer, Terratest, Terraform certifications, Terraform map type, Terraform Associate, Terraform: list type, TF_VAR_, TF_LOG, Terraform provider versioning, Terraform Style Conventions, Required version, Terraform plugin, Terraform Named Values, tags, Changelog, tfsec, tflint, Operators, Expressions: for, splat, Debugging, Namespaces, Terraform Landing Zones, CDKTF, Atmos

https://stackoverflow.com/a/57631204