In the year 1569, an expedition with a mixed Scandinavian crew under a captain Ingolfsson went to Africa, sailed down the coast along the Portuguese colonies, reached the Cape of Good Hope. They liked the climate and told king Alexander / Alasdair IV on their return about it. On his wish, the Scandinavians founded the colony of Australafrica (Australia for short) with the capital Alexandersborg (OTL Cape Town) in 1574.
1577, the Dutch started to make trade with Africa (always threatened, since this area was Portuguese turf), also reached Australia. For this time, they had to accept that the Scandinavians came first. But when Scandinavia fell into trouble after king Alexander's death, the Netherlands used the opportunity and occupied Australia in 1594.
They would face resistance, however. In 1600, the revolt of the "Söderlinger" (as Scandinavians in Australia called themselves) against Dutch started. When Sweden had consolidated, they made the "Australian War" 1615/16: Sweden defeated the Dutch, took back their still mostly Scandinavian-settled colony.
When Sweden allied with France in the Third Republican War, in 1792 troops of Britain landed in Australia. They stormed several cities and fortresses of the Söderlinger, but had to give them back after the end of the war.
In 1830, a Swedish ship coming from Australia discovered Antarctica.
When Germany toppled the Socialist government of Scandinavia, they also took control of Australia in 1880. A few years later, in 1884, the Gold Rush in Australia started. Many Germans, Swiss and Dutch came to the country, definitely changing the ethnic makeup of the country's white population, which was until then Swedish-dominated.