I have seen that if you have a ring $R$ which is also a field $F$ then its corresponding polynomial ring $R[x]$ is an Euclidean domain.
So I am looking for counter examples of the converse that when $R[x]$ is an Euclidean domain then R need not be a field. I am not really sure how to look for these examples. Maybe there is some trivial ones that I have overlooked? or some non trivial examples ?