A cutting insert according includes a first surface and a cutting edge. The first surface includes a first inclined surface and a projection. The first inclined surface includes a first region located close to a first corner portion, a second region located close to a second corner portion, and a third region located between the first region and the second region. The projection includes a first projection located close to the first corner portion and a second projection located close to the second corner portion. A first top portion of the first projection is located closer to the first corner portion than a first boundary portion between the first region and the third region, and a second top portion of the second projection is located closer to the second corner portion than a second boundary portion between the second region and the third region.

A cutting insert according includes a first surface and a cutting edge. The first surface includes a first inclined surface and a projection. The first inclined surface includes a first region located close to a first corner portion, a second region located close to a second corner portion, and a third region located between the first region and the second region. The projection includes a first projection located close to the first corner portion and a second projection located close to the second corner portion. A first top portion of the first projection is located closer to the first corner portion than a first boundary portion between the first region and the third region, and a second top portion of the second projection is located closer to the second corner portion than a second boundary portion between the second region and the third region.