Secure data transmission is essential to prevent unauthorized access and tampering during transit. HTTPS, which uses TLS (Transport Layer Security), provides encryption for data transferred over the network. In Python, libraries like requests and urllib3 support HTTPS out of the box. For custom server implementations, frameworks like Flask and Django support HTTPS with appropriate configuration. It’s important to use strong cipher suites and keep TLS libraries up to date to mitigate vulnerabilities. Additionally, validating SSL certificates prevents man-in-the-middle attacks.