Deneuve

Deneuve is the name of the third most famous detective in the world. From the beginning of the series, the actual Deneuve isn't present, with L using their name as an alias throughout numerous cases.

L tells the Task Force that he uses Eraldo Coil as well as Deneuve as aliases with the purpose of further concealing his identity, considering anyone is likely to contact either Deneuve or Coil, as they are the third and second most well-known detectives, respectively.

In Death Note: Another Note: The Los Angeles BB Murder Cases, it is revealed that Deneuve was, in fact, a real person before giving up their name to L, as L had won a detective war between L, Deneuve, and Coil. In the very same book, it was also stated that it is common knowledge, for the most part, that L, Deneuve, and Coil are the same person.