Some of my favourite ASX opportunities are businesses that have already proven themselves in Australia but still have enormous markets overseas to pursue.
If they can keep building their international presence, I think the three shares below could be considerably larger businesses in the years ahead.

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Breville Group Ltd (ASX: BRG)
Breville has turned an Australian appliance brand into a global premium kitchen business.
Its products now compete in major markets around the world, particularly across coffee and food preparation.
I think coffee is one of the most interesting parts of the opportunity.
Consumers have become increasingly willing to spend money on better coffee at home, and Breville has built a strong reputation for machines that sit between basic household appliances and much more expensive professional equipment.
That gives the company room to keep attracting people who want to recreate the café experience at home.
Breville can also grow by entering more countries, expanding its product range, and encouraging existing customers to buy additional products over time.
One thing I like is that the company does not need to become the dominant appliance company everywhere. Winning a larger share of premium kitchen spending across a growing collection of markets could be enough to support many years of expansion.
Catapult Sports Ltd (ASX: CAT)
Catapult Sports operates in a growing part of the technology industry.
Its technology helps professional sporting organisations analyse athlete performance, video, tactics, and other information used by coaches and performance teams.
I think there is a strong long-term reason for clubs to spend more in this area.
Elite sport is enormously competitive. Even small improvements in player preparation, recruitment, injury management, or tactical decision-making can be valuable when teams are trying to gain an advantage.
Catapult can keep expanding by signing more organisations, adding more teams within existing customers, and encouraging those customers to use more of its software and technology.
The company has also broadened its offering through areas such as video analysis and athlete scouting.
For me, that creates the opportunity for Catapult to become increasingly embedded in how professional sporting organisations operate.
There are major leagues, clubs, universities, and sporting programs across the world, so I think the addressable market still gives the business plenty of room to run.
Megaport Ltd (ASX: MP1)
Megaport gives businesses a way to connect their networks directly to cloud providers, data centres, and other digital infrastructure.
I think that becomes more valuable as companies rely on a growing number of cloud services.
Artificial intelligence (AI) could create another source of demand for Megaport's services.
AI workloads require enormous amounts of computing power and data to move between infrastructure. Businesses may need to connect to several cloud providers or specialised computing platforms rather than keeping everything in one place.
Megaport has also expanded into AI infrastructure through Latitude.sh, giving it exposure to customers looking for access to high-performance computing.
I like the broader idea here. As corporate IT infrastructure becomes more distributed, businesses need flexible ways to connect everything together. Megaport has built a global network specifically around solving that problem.
If cloud computing and AI infrastructure continue expanding, I think the amount of connectivity businesses require could grow substantially with them.
Foolish takeaway
I think Australian investors sometimes underestimate just how large the opportunity can become when an ASX-listed company succeeds internationally.
Breville, Catapult Sports, and Megaport already have businesses that extend well beyond Australia, but I think there is still plenty of territory left to capture.
I would be comfortable buying all three and giving their global ambitions years to play out.