Is masturbation a sin?

The Bible never directly names or addresses masturbation. That's worth saying plainly, since a specific verse is sometimes claimed to settle this. It doesn't.

A passage in Genesis about a man named Onan is often cited here. It's actually about something else: refusing a specific family duty to his brother's widow, not masturbation as a general category. Using it that way stretches the text past what it says.

Because Scripture doesn't address the act directly, Christians reason from broader principles instead. Is lust or objectifying fantasy involved? Is it becoming compulsive or hard to control? What does a person's own conscience conclude in good faith?

Sincere Christians land in different places here. Some see it as morally neutral in itself. Others see it as tied closely enough to lust to avoid. Most agree the bigger question is usually what's happening in someone's mind, not the act alone.