Is it true that the phrase 'is it true that' is grammatically correct?

Yes, the phrase 'is it true that' is grammatically correct. It follows a standard Yes-No question structure, consisting of three key components: 1) the auxiliary verb 'is', 2) the dummy subject 'it', and 3) the adjective complement 'true'. The subordinate clause, introduced by 'that', provides additional information or a statement. For example, in the sentence 'Is it true that the meeting has been canceled?', 'is it true' asks for confirmation of the truth of the proposition, while 'that the meeting has been canceled' is the clause being questioned. This structure is widely used in both formal and informal contexts. While some speakers may shorten it to 'Is ... true?' due to redundancy, 'is it true that' remains perfectly grammatical and widely accepted.