Livy (Titus Livius). Ab urbe condita
Divergence: 323 BCE
What if: Alexander the Great lived longer and turned west to attack the Romans.
Summary: A digression in book IX, sections 17-19, of this history of Rome patriotically suggests that the Romans would have beaten him.
Comments: The oldest alternate history? As one of the earlier parts of Livy's history, this digression was likely written around 35 to 30 BCE.
Published: Barbou 1775; Tauchnitz 1829; Clarendon 1960-1969.
Original in: Latin.
Translation: English by B.O. Foster as Ab urbe condita, Harvard University/Heinemann 1926, 1948, 1957, 1963, 1975, 1982 (0674992105w88 android, 0439991910).
Translation: English by Betty Radice as The History of Rome from Its Foundation, Penguin.
Translation: French by P. Du-Ryer as Ab urbe condita, Jore 1722.
Translation: French by Gaston Baillet as Ab urbe condita, Les Belles Lettres 1954.
Translation: German of excerpts as "Wenn Alexander der Große sich gegen Rom gewandt hätte", in Alexanders langes Leben, Stalins früher Tod und andere abwegige Geschichten: Erzaehlungen und Berichte aus Parallelwelten (ed. Erik Simon), q.v.
Translation: Portuguese by Paulo Matos Peixoto as História de Roma, Paumape 1990.