photographic paper; photo paper
Paper coated with light-sensitive chemicals, used for printing photographs in a darkroom or with a photo printer.
I print onto photographic paper in the darkroom.
This photo paper has a glossy finish.
印画紙 is a more technical term for photographic printing paper, often used in professional or darkroom contexts. 写真用紙 is a broader, more everyday term that can also refer to paper for inkjet photo printers.
Compound of 写真 (photograph) + 用紙 (paper for a specific use).