The IRS has outlined the Form 1040 series as the Federal income tax return forms. This includes forms such as 1040 (Resident Federal income tax return, 1040NR (Nonresident Federal income tax return), 1040X (Amended Federal income tax return), etc.
In case you are deemed as a nonresident for tax purposes by the IRS and you have earned US sourced income during the tax year, you may need to file form 1040NR to report your income and income tax withheld.