A long-sleeved T-shirt is a type of shirt, of a style and fabric similar to a T-shirt, although, of course, with long sleeves. Long-sleeved T-shirts first became popular in the 1970s as a thinner, more lightweight alternative to a sweatshirt. A long-sleeved t-shirt is sometimes worn underneath a short-sleeved shirt for warmth, typically in the fall and winter.
Although technically it could be considered a contradiction in terms, the term "long-sleeved t-shirt" has fallen into common usage.