What is antonym of a fake painting?

The antonym of a fake painting depends on what aspect of "fake" you're focusing on:

* If "fake" refers to authenticity:

* Authentic painting

* Genuine painting

* Original painting

* If "fake" refers to quality:

* Masterpiece

* High-quality painting

* Excellent painting

The best antonym depends on the specific context and what you are trying to convey.