。
I don't need dinner.
Literal
Dinner [topic-は] need-not-[polite-ません].
いる ('to need, to require') — distinct from いる ('to be/exist' for animates)! — takes the thing needed as a subject (usually が or は). いりません ('do not need') is its polite negative. Common in daily exchange: 'Do you want X?' 'いりません.' Short and declarative.