If you mean the Unicode "NO EQUAL TO" sign - like an = with a /
superimposed (you may not be able to see this: ≠), it has hex code 2260
and is available in e.g. modern versions of Arial, Times new Roman and
so on.
If you mean the workarounds typically used in programming languages,
e.g. <> or !=, they are usually composed of the two separate characters,
i.e. < and > or ! and =. (I don't know if there is a single Unicode
character for either of those two.)