1. United Kingdom: British Empire.
2. Spain: Spanish Empire.
3. Portugal: Portuguese Empire.
4. France: French Colonial Empire.
5. Netherlands: Dutch Empire.
6. Belgium: Belgian Colonial Empire.
7. Italy: Italian Colonial Empire.
8. Germany: German Colonial Empire.
9. China: Various dynasties with significant influence and regional control.
10. Mongol Empire (across parts of Asia and Europe).
11. Roman Empire (ancient Rome's extensive conquests).
12. Greek City-States (Athens, Sparta, Macedonia had regional control in ancient times).
13. Russian Empire (vast expansion over Eastern Europe and Central Asia).
14. Ottoman Empire (controlling substantial parts of the Balkans, Middle East, and North Africa).
15. Maurya Empire (ancient India, significant territorial influence).
16. Persian Empire (series of empires with considerable reach across ancient Western Asia).
17. Mughal Empire (dominating most of the Indian subcontinent during medieval times).
18. Aztec Empire (pre-Columbian Mesoamerican empire centered in present-day Mexico).
19. Inca Empire (powerful South American empire during pre-Columbian times).
20. United States: While not typically labeled as an "empire," the United States has exercised significant geopolitical influence worldwide.
This list is not exhaustive, and historical territorial acquisitions, control, and influences varied within each country's specific periods of imperialism.