| Country Name | Sea Name | Number of Ports | * Introductions in Ports |
|---|---|---|---|
| Tunisia | Baltic Sea | ||
| Turkey | Baltic Sea | ||
| Turkmenistan | Baltic Sea | ||
| Turks and Caicos Islands | Baltic Sea | ||
| Tuvalu | Baltic Sea | ||
| Ukraine | Baltic Sea | ||
| United Arab Emirates | Baltic Sea | ||
| United Kingdom (Britain) | Baltic Sea | 6 | |
| Uruguay | Baltic Sea | ||
| USA | Baltic Sea | ||
| Vanuatu | Baltic Sea | ||
| Venezuela | Baltic Sea | ||
| Vietnam | Baltic Sea | ||
| Virgin Islands, U.S. | Baltic Sea | ||
| Wallis and Futuna | Baltic Sea | ||
| Western Sahara | Baltic Sea | ||
| Yemen | Baltic Sea |