Direct Opposites:
* Irrelevant: This is the most direct opposite, meaning not related to the matter at hand.
* Unrelated: Similar to irrelevant, but emphasizes a complete lack of connection.
* Extraneous: Something that is outside the main subject and therefore unnecessary.
Other Antonyms:
* Tangential: Only slightly connected to the main subject, going off on a side track.
* Digressive: Moving away from the main topic in a rambling manner.
* Inapplicable: Not fitting or relevant to the situation.
* Off-topic: Clearly not related to the discussion or subject.
* Beside the point: Missing the main point or purpose of the conversation.
* Superfluous: More than is needed or wanted; unnecessary.
The best antonym for "germane" will depend on the specific context.