An officiant is someone who is authorized to perform religious ceremonies. The officiant may have a specific title.
In the US the word ‘celebrant' is often used interchangeably with the word ‘officiant', however, there is a slight difference!
An officiant refers to an individual – a priest or minister, for example – acting in a religious capacity. A celebrant is someone authorized to officiate a wedding ceremony that may or may not be religious (i.e. civil).
Subtle…but different. 😉