Did Alexander the Great speak Macedonian?

Of course Alexander spoke Macedonian, which was a dialect of Greek.

“The language of the Macedonians was a distinct and particular form of Greek, resistant to outside influences and conservative in pronunciation. It remained so until the fourth century when it was almost totally submerged by the flood tide of standardized Greek.” (Nicholas Hammond, British scholar and expert on Macedon, “A History of Macedonia”, Vol. ii, 550-336 BC)

“The evidence for the language of the Macedonians has been reviewed and discussed by Kalleris and Hammond, Griffith, and many others, all contending that it was a dialect of Greek. The increasing volume of surviving public and private inscriptions makes it quite clear that there was no written language but Greek. There may be room for argument over spoken forms, or at least over local survivals of earlier occupancy, but it is hard to imagine what kind of authority might sustain that. There is no evidence for a different “Macedonian”language that cannot be as easily explained in terms of dialect or accent.” (“Cambridge Ancient Histories”, Cambridge Univ. Press, 1998)

The Digital Library of Language Relationships, classifies Macedonian as a Hellenic (Greek) language. Not to be confused with the modern North Macedonian language, which is related to the Bulgarian language:

“Name: Ancient Macedonian.

Parent Subgroup: Hellenic (Greek).

Brief Description: The ancient language of the Macedonian kingdom in N. Greece and modern Macedonia during the later 1st millennium BC. Survived until the early 1st millennium AD. Not to be confused with the modern Macedonian language, which is a close relative of the Slavic Bulgarian (MultiTree: A Digital Library of Language Relationships: Ancient Macedonian)

You may also wish to go ahead and read Ancient Macedonian as a Greek dialect: A critical survey on recent work (Greek, English, French, German text) 

Summing up,

“We know the ancient Macedonians were fundamentally Greeks. That is to say they were Greek speakers and ethnically they were Greeks.” (Yale University, “Introduction to Ancient Greek History, Philip, Demosthenes and the Fall of the Polis”, 2007)
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