Long Acre Square, as it was originally known. Says so right on the card, too - which just shows how much you should trust them. This postcard is dated 1910, but the Square had been renamed "Times Square" by 1904. Apparently the vendor did not throw out his stock when the change was made.

In the middle, of course, is the Times Tower; to the right, the Hotel Astor. In the background to the left, the New York theater, part of Oscar Hammerstein's massive Olympia theater.
..