What is the opposite of mysterious?

The opposite of mysterious depends on what aspect of "mysterious" you're focusing on. Here are some possibilities:

If you're thinking of "mysterious" as meaning "unclear, puzzling, or difficult to understand":

* Clear

* Obvious

* Plain

* Simple

* Straightforward

* Understandable

* Explicable

If you're thinking of "mysterious" as meaning "secretive, enigmatic, or concealed":

* Open

* Transparent

* Honest

* Forthright

* Revealing

* Explicit

If you're thinking of "mysterious" as meaning "surprising, unexpected, or strange":

* Expected

* Ordinary

* Normal

* Familiar

* Predictable

* Commonplace

The best opposite for "mysterious" depends on the specific context.