You must specify a region. You can also configure your region by running 'aws configure'

What causes this

The AWS CLI or SDK doesn’t know which AWS region to send your request to. Every AWS API call targets a specific region, and if none is configured, the request fails.

This happens when:

• You never ran aws configure after installing the CLI
• The AWS_DEFAULT_REGION environment variable isn’t set
• Your ~/.aws/config file is missing or doesn’t have a region for the active profile
• You’re using a named profile that doesn’t have a region configured
• Your CI/CD environment doesn’t set the region

Fix 1: Set the region with aws configure

aws configure
# AWS Access Key ID: (enter your key)
# AWS Secret Access Key: (enter your secret)
# Default region name: us-east-1
# Default output format: json

This writes to ~/.aws/config and ~/.aws/credentials.

Fix 2: Pass the region flag directly

aws s3 ls --region us-east-1
aws ec2 describe-instances --region eu-west-1

This overrides any configured default for that single command.

Fix 3: Set the environment variable

# For the current session
export AWS_DEFAULT_REGION=us-east-1

# Or permanently in your shell config
echo 'export AWS_DEFAULT_REGION=us-east-1' >> ~/.bashrc
source ~/.bashrc

For zsh:

echo 'export AWS_DEFAULT_REGION=us-east-1' >> ~/.zshrc
source ~/.zshrc

Fix 4: Configure a named profile

# ~/.aws/config
[default]
region = us-east-1

[profile staging]
region = eu-west-1

[profile production]
region = us-east-1

Use a profile:

aws s3 ls --profile staging
# or
export AWS_PROFILE=staging

Fix 5: Set region in your SDK code

If you’re using the AWS SDK in code:

// AWS SDK v3 (JavaScript)
import { S3Client } from '@aws-sdk/client-s3';

const client = new S3Client({ region: 'us-east-1' });

# boto3 (Python)
import boto3

client = boto3.client('s3', region_name='us-east-1')

Fix 6: Fix CI/CD environments

In GitHub Actions:

env:
  AWS_DEFAULT_REGION: us-east-1

In Docker:

ENV AWS_DEFAULT_REGION=us-east-1

How to prevent it

• Always run aws configure right after installing the AWS CLI
• Set AWS_DEFAULT_REGION in your shell profile as a fallback
• In CI/CD, always explicitly set the region — don’t rely on defaults
• Use named profiles for different environments so each has its own region
• When writing SDK code, always pass the region explicitly rather than relying on environment config