How to fix Error: Required variable not set in Terraform

Run terraform plan or apply with the -var flag to supply the variable value directly:

terraform plan -var="variable_name=value"
terraform apply -var="aws_region=us-east-1"

For multiple variables, use multiple -var flags:

terraform plan -var="region=us-west-2" -var="environment=prod"

Create a file named terraform.tfvars (or terraform.tfvars.json) in your working directory with variable assignments:

# terraform.tfvars
aws_region = "us-east-1"
environment = "production"
access_key = "your-key-here"

Terraform automatically loads this file. To use a custom filename, include the -var-file flag:

terraform plan -var-file="prod.tfvars"

Set environment variables in the format TF_VAR_<variable_name> before running Terraform:

export TF_VAR_aws_region="us-east-1"
export TF_VAR_environment="production"
terraform plan

On Windows, use set instead of export:

set TF_VAR_aws_region=us-east-1
terraform plan

If the variable should have a sensible default, add it to the variable block in your variables.tf file:

variable "aws_region" {
  type    = string
  default = "us-east-1"
}

variable "environment" {
  type    = string
  default = "dev"
}

With defaults, the variable becomes optional at runtime.

Ensure all variables you're trying to use are declared in a variables.tf or main.tf file:

variable "required_var" {
  type        = string
  description = "This variable is required"
  # No default value means it must be supplied
}

If the variable block doesn't exist, create it before trying to set its value.

If using Terraform Cloud or Terraform Enterprise, variables must be set in the workspace's Variables section:

1. Go to your workspace in the UI
2. Click Variables
3. Add the variable name (e.g., 'aws_region') with its value
4. Select 'Terraform variables' (not 'Environment variables') category
5. Save and rerun your plan/apply

Also verify that the workspace's Working Directory is set correctly under Settings > General.