Nah, it no gambit
Is the Queens Gambit a gambit?

Yes, if both sides want to play it like a gambit. As Anish Giri said, you can't play a gambit if the other side refuses to accept the material. And in the Queen's Gambit, White can play in the spirit of a gambit (3.e4 or similar lines) or not. Both sides must be willing to play the gambit.

It's funny, but nobody was able to prove that it is a true gambit https://www.chess.com/forum/view/general/the-queens-gambit-is-not-a-gambit-change-my-mind
It's like giving someone a gift, and after that, without any problems, return it, before telling everyone how generous and courageous you were.

It's funny, but nobody was able to prove that it is a true gambit https://www.chess.com/forum/view/general/the-queens-gambit-is-not-a-gambit-change-my-mind
It's like giving someone a gift, and after that, without any problems, return it, before telling everyone how generous and courageous you were.
Saying that "nobody was able to prove that it is a true gambit" doesn't make it so.
A gambit is an offer of material in the opening in exchange for development or space. 1.d4 d5 2.c4 dxc4 3.e4 is a true gambit by definition.

It's funny, but nobody was able to prove that it is a true gambit https://www.chess.com/forum/view/general/the-queens-gambit-is-not-a-gambit-change-my-mind
It's like giving someone a gift, and after that, without any problems, return it, before telling everyone how generous and courageous you were.
Saying that "nobody was able to prove that it is a true gambit" doesn't make it so.
A gambit is an offer of material in the opening in exchange for development or space. 1.d4 d5 2.c4 dxc4 3.e4 is a true gambit by definition.

@Talis204, just about no White player enters the Queen's Gambit accepted and plays Qa4+. According the Chessbase, Masters play 3.Qa4+?! about 1% of the time.
Even after 3.e3, Black can strive to hang on to the pawn with the computer move Be6. That isn't a good move, but it doesn't mean the QGA isn't a gambit.

@Talis204, just about no White player enters the Queen's Gambit accepted and plays Qa4+. According the Chessbase, Masters play 3.Qa4+?! about 1% of the time.
Even after 3.e3, Black can strive to hang on to the pawn with the computer move Be6. That isn't a good move, but it doesn't mean the QGA isn't a gambit.
It doesn't matter, how often they play it. It just shows that this is not a 'true' gambit. And Qa4 doesn't seem to be bad - it's definitely not the best move here, but White still has no problems with their position - at least they got two central pawns.

No it's not, since what White wants to achieve with this opening is basically the opposite of what is aimed for with all other gambits (namely aggression and tactical play):
The queen gambiteer wishes closed positions with the most boring passive games imaginable and try to actually prevent black to develop a single piece, attacking every time with the same plans (Bd3 Qc2 etc).

It's funny, but nobody was able to prove that it is a true gambit https://www.chess.com/forum/view/general/the-queens-gambit-is-not-a-gambit-change-my-mind
It's like giving someone a gift, and after that, without any problems, return it, before telling everyone how generous and courageous you were.
Saying that "nobody was able to prove that it is a true gambit" doesn't make it so.
A gambit is an offer of material in the opening in exchange for development or space. 1.d4 d5 2.c4 dxc4 3.e4 is a true gambit by definition.
White forcefully gets his pawn back in a couple moves, which is not true in other actual gambits.
Do you think it's a gambit, or does it not count because white can easily win back the pawn?