The 36-year-old has been named among the 18 referees for next summer’s European Championship finals in France.
The Lanarkshire schoolteacher told www.scottishfa.co.uk: “I’m really looking forward to it and can safely say that this is likely to be the highlight of my refereeing career.
“It’s the closest a referee can ever come to getting picked for Scotland.
“You can imagine what it’s like for a player to play in a major championship and it’s the same for the referees. It will be a great honour to represent my country on such a world stage.”
Collum’s appointment comes months after he refereed the William Hill Scottish Cup final and the UEFA Super Cup final between Barcelona and Sevilla.
Collum said: “All these experiences have contributed to making me the referee I am today. Scottish football has got me to the position I am in today at UEFA. You need to be performing domestically and you need to be challenged and I feel that’s the case.
“All these big matches, that as a young referee I would never have dreamt of being involved in, will certainly help contribute to that experience at a finals tournament.”
But he has not always been so highly thought of in Scotland, with Hearts head coach Robbie Neilson revealing his team trained with 10 men ahead of their trip to Hamilton in August after hearing Collum and his team of officials were in charge. Hearts full-back Callum Paterson was sent off as the visitors lost 3-2 and the red card was subsequently rescinded.
Collum’s five-strong team has not been announced but the majority are expected to come from Scotland, whose football team will not be present at Euro 2016 after finishing fourth in their qualifying group.
John Fleming, the SFA’s head of referee operations, said: “Firstly, I am absolutely delighted for William. He is a tremendously hard-working referee and this is great news for the country.
“There are only 18 referees who have been appointed, and for Scotland to have one of those is fantastic news.
“I’m sure the country will get behind William and his team in the summer.”