While he didn't actually discover radiation itself (since it exists naturally), he was the first to observe and document the phenomenon of X-rays, which are a form of electromagnetic radiation.

It's important to note that other scientists were investigating similar phenomena at the time, such as Henri Becquerel, who discovered radioactivity in 1896.

Röntgen's discovery was groundbreaking and revolutionized the field of medicine, leading to the development of X-ray imaging, which is still widely used today.