A tape cassette includes a generally rectangular housing, a tape, an opening, and a roller. The housing has a top wall and a bottom wall. The top wall includes a top surface, a lower surface and a connection portion connecting. The housing defines first, second, third, and fourth corner portions. The lower surface includes a first portion between the connection portion and a side of the second corner portion and a second portion between the connection portion and a rear of the second corner portion with a space between the first portion and the second portion. An intersection of the connection portion and the lower surface includes a third portion that is a part of an edge forming the space between the first portion and the second portion.