A transcontinental country isn't just a country near a continental boundary. It's one whose actual land is split across two continents by the line geographers use to separate them. Three countries fit that description clearly enough that there's little debate about it: Russia, Türkiye, and Egypt.
Russia: mostly Asian land, mostly European population
The conventional boundary between Europe and Asia runs along the Ural Mountains and the Ural River, then down to the Caspian Sea. Everything west of that line, including Moscow and St. Petersburg, is geographically Europe. Everything east, including Siberia and the Russian Far East, is Asia. By land area, the Asian side is dramatically larger, around three-quarters of the country. By population, it's the reverse: the large majority of Russians live on the European side, west of the Urals.
Türkiye: one city split by a strait
Türkiye's split is smaller in area but more visible day to day. The Bosphorus strait runs directly through Istanbul, with part of the city on the European side and part on the Asian side, connected by bridges and a tunnel that people commute across every day. The rest of European Türkiye is the region of Thrace, a relatively small area in the country's northwest. The overwhelming majority of the country's land, called Anatolia, is in Asia.
Egypt: almost entirely African, except for one peninsula
Egypt is the simplest case geographically. Nearly the entire country, including Cairo and the Nile Valley, sits in Africa. The exception is the Sinai Peninsula, on the far side of the Suez Canal, which is part of Asia. The Suez Canal itself is often treated as the dividing line, making it one of the few places in the world where a single human-made waterway marks a continental boundary.
Cases that get mentioned but are murkier
A few other countries show up in discussions of transcontinental status, usually for weaker or more disputed reasons. Kazakhstan has a small portion of territory west of the Ural River by some definitions, though it's conventionally classified as entirely Asian. Georgia and Azerbaijan straddle the Caucasus region, which different sources draw the Europe-Asia line through differently. Indonesia spans two geological plates and is sometimes described as split between Asia and Oceania, though it's conventionally grouped entirely within Asia. None of these is treated as transcontinental in this site's own classification, which follows the more conventional, narrower definition: Russia, Türkiye, and Egypt only.
- In Country Locator and the Continents quiz here, all three transcontinental countries are included in the practice pool for both of their continents, so you'll see Russia show up under both Europe and Asia practice.
- Their capital, flag, currency, and other facts are listed once, since those don't change depending on which continent you're practicing.
Sources: CIA World Factbook, country profiles for Russia, Türkiye, and Egypt; National Geographic Society, "Continent."