Yes, a fossil. It's a broken section from a crinoid columnal. Those with columnar 'stalks' are sometimes called 'sea lilies' because of their resemblance to plants, but they're marine animals loosely related to starfish and sea urchins. That's the reason they sometimes have that five-pointed star shape in the centre of the columnal... because they share an evolutionary history with respect to ancestral forms. They date from the Ordovician period (around 480 million years ago) onwards and are not extinct today but there are no fossils known which are beyond the Late Triassic of c.200 mya.
EDIT: OtB beat me to it.