Guadiana

The third one in Top 10 Longest Rivers in Portugal that Toplist would like to introduce to you is Guadiana. The Guadiana River, sometimes known as the Odiana, is a lengthy section of the Portugal-Spain border that separates Extremadura and Andalusia (Spain) from Alentejo and Algarve (Portugal) (Portugal). The river and its tributaries run from east to west, then south through Portugal to the border towns of Vila Real de Santo António (Portugal) and Ayamonte (Spain), where they pour into the Gulf of Cádiz. It is the fourth-longest river in the Iberian Peninsula, covering 829 kilometers (515 miles), and its hydrological basin encompasses around 68,000 square kilometers (26,000 square miles) (the majority of which lies within Spain).

Between Vila Real de Santo António (Portugal) and Ayamonte (Portugal), the Guadiana flows east to west through Spain and south through Portugal, forming the Spanish-Portuguese border. It then flows into the Gulf of Cádiz, which is part of the Atlantic Ocean (Spain). It stretches for 818 kilometers (508 miles), with 578 kilometers (359 miles) within Spanish territory, 140 kilometers (87 miles) within Portuguese territory, and 100 kilometers (62 miles) shared by the two countries. Roughly 82 percent of its basin, or 55,444 square kilometers (21,407 square miles), is in Spain, while about 17 percent, or 11,560 square kilometers (4,460 square miles), is in Portugal.

Length: 818 km (508 mi- shared with Spain)