Start with Ballad of the Salt Sea. It is the 1967 serial that introduced the character, and the only full-length Corto Maltese story: the South Pacific in 1913, a Melanesian pirate confederation, and Corto himself introduced tied to a raft. Every shorter album assumes the things this one establishes, and it is the single place Pratt takes his time.
The alternative most readers stumble into is whichever album their shop happens to stock, usually Corto Maltese in Siberia or Fable of Venice, because those are the famous ones. Both are better books than the Ballad and both are much harder to enter cold. Pratt's method is ellipsis — the decisive action frequently happens between panels, and you are expected to infer it — and starting on a short album means learning that method and the character at the same time.
Before you buy: the edition problem
This is the practical thing to know first. The albums have appeared in English under at least three publishers, with different titles, different trim sizes, and some in black and white and some coloured. Several albums exist twice in our catalogue under two different names, and readers buy the same story twice without noticing.
The clearest cases: Celtic tales was published by NBM as The Celts, and both records exist. The Ethiopian appeared in an earlier NBM edition as Corto Maltese in Africa. Ballad of the Salt Sea is held here in the NBM edition, and a later IDW edition of the same story exists under a slightly different title and with a different colour treatment. Check the contents, not the cover, before you order.
The short-story albums, in order
This is where Pratt does his best work, and the four books are sequential. Under the sign of Capricorn is the first collection, set around the Caribbean and the Guianas in 1916 and 1917, and it is where the series finds its real form — eight to twenty pages a story, most of the plot implied. Beyond the windy isles is the weakest of the four and sets up the two that follow. Celtic tales takes Corto to Ireland and the Western Front during the First World War and is the best-regarded of the group. The Ethiopian holds four stories set in Africa and Arabia in 1918.
The long journeys
The album-length adventures of the 1970s, where the historical background becomes as important as the plot. Corto Maltese in Siberia is Manchuria and the Russian Civil War, with the Red Lanterns, Baron Ungern-Sternberg and a train full of gold; it is often named as the peak of the series and it carries the most historical scaffolding. Fable of Venice is Venice in 1921 under the early Fascists, with freemasonry and an emerald, and it is the most personal of the albums — Pratt grew up there. It is also the most elliptical, and you should expect to finish it unsure what happened, which is deliberate rather than a translation problem. The golden house of Samarkand sends him through Turkey, the Caucasus and Central Asia after Alexander's treasure, and is the most conventionally adventurous of the late books.
Late Pratt, the prequel, and what is missing
Tango all at half-light is Buenos Aires in 1923 and the darkest album, as much about Argentine politics as about Corto. Corto Maltese: The Early Years is the prequel, drawn late — the Russo-Japanese War, Jack London, Rasputin — and it belongs last rather than first, because its whole effect depends on already knowing the man it describes.
Be aware that this is ten of the twelve albums. The Secret Rose and Mu close the series and do not resolve to any catalogue record we can verify, so they are absent here rather than omitted by choice. You will need to source those two separately if you want the sequence complete.
The Corto Maltese path lays the same order out album by album with the edition notes attached.
Follow the full ordered path here: Corto Maltese Reading Order: Where to Start Hugo Pratt's Adventure Comics.