Hello,
If you're a British citizen and your fiancé is a Canadian citizen, he likely won't need a visa to enter the UK for your wedding as long as your stay is less than 6 months.
Indeed, Canadian citizens are exempt from needing a visa for short visits (up to 6 months) to the UK, provided they:

• Have a valid Canadian passport.
• Intend to leave the UK at the end of their visit.
• Have no intention of working or studying in the UK.
• Have sufficient funds to support themselves during their stay.

Therefore, if your fiancé meets these conditions and your wedding and stay in the UK are less than 3 months, you should not have any issue.
You can check the latest regulation here: https://www.gov.uk/check-uk-visa

VERY IMPORTANT: Remember to give the required notice of marriage to a registrar's office in the UK at least 28 days in advance.

NB: Even if your fiancé doesn't need a visa, he might still want to apply for a Marriage Visitor Visa if they plan to stay in the UK for more than 6 months or want to switch to another visa type after the wedding.
More information here: https://www.gov.uk/marriage-visa