と言(い)うのは事実(じじつ)だ

～というのは事実(じじつ)だ is a phrase used to strongly express that (A) is something that is 'true', 'a fact', or has 'no doubt'. というのは may be used after almost any phrase, before the noun 事実(じじつ) 'truth', paired with the auxiliary verb だ (or です) will determine that phrase to be a fact.

• この人(ひと)が私(わたし)の母親(ははおや)を殺(ころ)したというのは事実(じじつ)だ。
  It is a fact that this person killed my mother.
• 彼女(かのじょ)が弁護士(べんごし)というのは事実(じじつ)だ。
  It is a fact that she is a lawyer.

The literal translation というのは事実(じじつ)だ is 'that which is (A) is true', as (A) is just a nominalized phrase. It is also quite common to see this expression with という omitted, the only difference being that it sounds slightly weaker.

• 赤信号(あかしんごう)を無視(むし)したのは事実(じじつ)だ。
  It is true that I ignored the red light.
• 彼女(かのじょ)と仲直(なかなお)りしたのは事実(じじつ)だ。
  It is a fact that I worked it out with my girlfriend.