Yes, a 1×1 matrix is considered a square matrix.
A square matrix is defined as a matrix that has the same number of rows and columns. In the case of a 1×1 matrix, it has one row and one column, which satisfies the condition of having equal dimensions. This makes it a special case of a square matrix.
Moreover, a 1×1 matrix can also be seen as a single number, or a scalar, which further emphasizes its square nature. In linear algebra, square matrices play a significant role, and the 1×1 matrix is the simplest form of such matrices.