Sh2-157, also known as the Lobster Claw Nebula, is a bright emission nebula located in the constellation Cassiopeia. It is part of the Sharpless catalog of H II regions, which are areas of ionized gas that glow due to intense radiation from nearby young, hot stars.

The nebula has a distinctive shape that has earned it its marine-inspired nickname. It features intricate filaments of gas and dust and contains several star-forming regions and is associated with clusters of young, massive stars.  The nebula's glow comes from ultraviolet radiation emitted by massive stars, which ionize the surrounding hydrogen gas.

Sh2-157 is approximately 8,000 light-years away from Earth.  Open cluster NGC7510 is located nearby, along with a host of other notable nebulae and molecular clouds.