If you were worried Prince Harry's been feeling left out with all this talk of Prince William's wedding, fear not! Wills has chosen him to be best man.
Best man at a wedding is a big job - you have to look after the bride and groom's wedding rings AND you have to make a big speech afterwards.
Kate Middleton's sister Philippa will be her maid of honour.
The couple will marry at Westminster Abbey on Friday, 29 April, and it's going to be a bank holiday.
Kate said she's happy but slightly daunted about joining the Royal family.
Watch the Royal couple talking about their engagement
Prince William is second in line to the throne.
The couple met at St Andrews university in Scotland, nine years ago.
The prince asked Kate's dad for permission to marry his daughter and the Queen has also given the couple her blessing, saying she's "absolutely delighted" for the pair.
After the couple are married, they will live in north Wales while the prince continues working as a helicopter pilot with RAF search and rescue for the next three years.