。
That much goes without saying.
Literal
Such-a thing [topic-は] without-saying [copula-だ].
言わずもがな is a literary set phrase for 'it goes without saying / needless to say,' formed from the classical negative conjunctive 言わず 'without saying' + もがな (a classical volitional particle for 'would that...'). Frozen as an idiom now and used as a noun or na-adjective. The sentence is very short but encapsulates a stiff literary expression.