If another artist paints a very similar painting, very obviously based on my original painting, do I have recourse?

It depends on the painting. If five painters set up their easels at or near the same spot and each paint faithful renditions of Mount Rainier then all five paintings will be remarkably similar -- and a separate copyright will attach to each. Works of art that creatively reproduce original old things do not infringe the past works that also reproduced those old things.

But if your "own design" does NOT exist in nature and someone has created a painting that's "substantially similar" to yours such that "an average lay observer would recognize the alleged copy as having been appropriated" from yours, then you have a legitimate complaint. To prevail, you must establish that the other painter (1) had access to your painting and (2) that his or her painting is substantially similar to yours.

Your challenge is deciding how much time and money to invest in seeking a remedy and, if any, then how to go about confronting the other painter. Only you know the potential impact on your business of having this (alleged) infringer selling paintings that are substantially similar to yours. Only you know the resources that you can bring to bear to address this matter. Only you know the effect on your reputation in the arts community and art buying public of making this an issue. Only after answering these questions will you know whether its makes sense to follow up. Copyright attorneys -- and intellectual property litigators -- charge about $300 per hour. It does not take long to spend more than your principles can afford.

One thing IS set in stone: if you have not already, you need to apply to register the copyright in your painting. Visit copyright.gov and read its Circular 40. And then hire a copyright attorney to fill out and send in the application (once you see how it's done, you can use that application as a template for others). Good luck.

It sounds like you have a copyright claim for this unauthorized copying of your painting. The infringer is competing with you in the same market, and if you're right that no one would disgaree that the works are substantially similar, you could sue for infringement.

As a practical matter, in order to sue you'd have to register your work with the Copyright Office, and your damages would be for the one infringing painting (unless there are others similarly infringed). So how it turns out is you spent a lot of time creating your painting, and the infringer spent almost as much time copying your painting, and your damages are limited accordingly. If the infringer were making lithographs of your painting and selling them as posters, they'd be doing much less work and you'd have much bigger damages.

Perhaps your most practical remedy is a letter letting the infringer know that you know about their copying, demanding that they turn over the profits of the copied work to you, and that they cease and desist in the future from such infringement.

Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship