In several articles it is reported that Nikola Tesla owned 700 patents (one article states he had 600 to 700 patents).

According to a recent study by the IEEE, an organization that Tesla once belonged to:

Newly Discovered Tesla Patents: In this paper are presented the results of a continuation of the investigation aiming to discovery and identify the previously unknown Nikola Tesla's patents. The investigation has shown that Nikola Tesla had at least 308 patents originating from 27 different countries. Though the newly discovered patents are members of the previously defined patent families, they give a new insight into his activities on the protection of the inventions on the international level, especially at the their beginning. The subject matter of 28 newly discovered patents from 7 various countries are different Tesla's inventions in the fields both of electrical and mechanical engineering.

It is possible that Nikola Tesla exaggerated the number of patents he had, although this seems unlikely given his character. More likely is that Tesla did file nearly 700 patents, and considering their importance to the military, the patents were classified and removed from public view. Also, considering all the claims Tesla had made for his unusual technologies, many of these technologies which later appeared in the arsenal of the US and foreign militaries, it is likely that nearly 400 of his patents are still hidden from public view.