The "User is Not Authorized to Overbook" error in Amazon Athena typically occurs due to insufficient IAM permissions. To resolve this issue, ensure that your AWS Identity and Access Management (IAM) policy grants the necessary permissions for Athena queries and overbooking operations. Start by checking the IAM policy attached to your user or role and update it to include the required permissions, such as athena:StartQueryExecution and athena:GetQueryResults. Additionally, verify that the policy allows access to the relevant S3 bucket where Athena stores query results of athenaidx user is not authorized to overbook. If using AWS Lake Formation, confirm that the user has appropriate permissions to the database and tables. Once the permissions are updated, retry the query execution. If the issue persists, consult AWS CloudTrail logs to identify any denied requests and refine the IAM policy accordingly.