Yes, you do. For US citizens, the most common one is the travelers visa which is valid for 30 days. Please visit the below link for more information. If you were initially an Indian citizen, please apply for an OCI if you don't have one. If you do have an OCI, please ensure it does not expire soon along with your passport. https://indianvisaonline.gov.in/evisa/tvoa.html
Check out the handy India travel guide! Go to the Travel & Guide tab or use this link: https://bit.ly/aswinharini