Siege of Szigetvár: Despite having killed Sultan Suleiman I the Magnificent a few days earlier in a surprise raid, the Hungarians lose to Turkish forces. There are, however, heavy losses on both sides — including both commanders.
A primary goal in this assault on the Szigeth Fortress in Baranya is to open a clear path for future invasions into Austria. Hungary ceased to be an independent nation after the Battle of Mohács in 1526, but the countryside is still not entirely subdued, and that's another goal of the Ottoman forces.
Because the Ottoman losses are so great — at least 20,000, according to most estimates — and because Sultan Sulieman the Magnificent is among the dead, this battle is the farthest the Ottomans are able to go this year, and they aren't able to make their planned march on Vienna.
This provides the Hapsburgs significant breathing room because Vienna will not be attacked by the Ottoman Empire again until 1683.