Ibn Rustah (in Persian: احمد ابن رسته اصفهانی - Aḥmad ebn Roste Eṣfahānī, also spelled Ibn Rusta, Ibn Ruste) was a 10th-century Persian explorer and geographer born in Rosta district, Isfahan, Persia. He wrote a geographical compendium known as Book of Precious Records. The information on his home town of Isfahan is especially extensive and valuable. Ibn Rustah states that, while for other lands he had to depend on second-hand reports, often acquired with great difficulty and with no means of checking their veracity, for Isfahan he could use his own experience and observations or statements from others known to be reliable. Thus we have a description of the twenty districts (rostaqs) of Isfahan containing details not found in other geographers' works. Concerning the town itself, we learn that it was perfectly circular in shape, with a circumference of half a farsang, walls defended by a hundred towers, and four gates.
His information on the non-Islamic peoples of Europe and Inner Asia makes him a useful source for these obscure regions (he was even aware of the existence of the British Isles and of the Heptarchy of Anglo-Saxon England) and for the prehistory of the Turks and other steppe peoples.
He wrote of tenth-century city of the Rus':
- "As for the Rus, they live on an island … that takes three days to walk round and is covered with thick undergrowth and forests; … They harry the Slavs, using ships to reach them; they carry them off as slaves and … sell them. They have no fields but simply live on what they get from the Slav's lands … When a son is born, the father will go up to the newborn baby, sword in hand; throwing it down, he says, 'I shall not leave you with any property: You have only what you can provide with this weapon.'" 
His impression of the Rus' is very favourable:
- "They carry clean clothes and the men adorn themselves with bracelets and gold. They treat their slaves well and also they carry exquisite clothes, because they put great effort in trade. They have many towns. They have a most friendly attitude towards foreigners and strangers who seek refuge."
This is in contrast to the account of Ibn Fadlan, whose views on hygiene (based on Islamic teachings on cleanliness and Islamic medical knowledge) contrasted with that of the Rus'. He noted that while the Rus' combed their hair and washed daily, they did so from the same bucket of water (which disgusted him personally). Ibn Fadlan also notes that slaves were not mistreated by the Rus'.
Of ancient Croatia he wrote in the chronicle Al-Djarmi:
- "Their ruler is crowned … He dwells in the midst of the Slavs … He bears the title of 'ruler of rulers' and is called 'sacred king'. He is more powerful than the Zupan (viceroy), who is his deputy … His capital is called Drzvab (Zagreb) where is held a fair of three days every month."
About a certain king of the Caucasus Ibn Rustah wrote:
- "He prayed on Fridays with the Muslims, on Saturdays with the Jews, and on Sundays with the Christians. 'Since each religion claims that it is the only true one and that the others are invalid', the king explained, 'I have decided to hedge my bets.'"
He also traveled extensively in Arabia and is one of the early Persian explorers to describe the city of Sana'a. In his Book of Precious Records, he writes:
- "It is the city of Yemen — there not being found in the highland or the Tihama or the Hijaz a city greater, more populous or more prosperous, of more noble origin or more delicious food than it. … San'a is a populous city with fine dwellings, some above others, but most of them are decorated with plaster, burned bricks, and dressed stones."
- Ibn Rustah was identified with the writer ibn Dasta, by Mihály Kmoskó (1876–1931).
- National Geographic, March 1985.