Where does the last name Constantino come from?

Question:I found an ancestor with the last name Constantino who lived in the French colony St. Genevieve in Missouri in the late 18th Century.

Best Answer - Chosen by Asker: I found an ancestor with the last name Constantino who lived in the French colony St. Genevieve in Missouri in the late 18th Century.

You cannot say for CERTAIN that any name comes from just one place.. it has to be worked back from the person himself, and where his ancestry is/ was.
I do use www.familysearch.org to check names.. since they use actual records (ie church baptisms, etc). Some of them show Italy as a place where the name is found. I also noticed a number of entries with the spelling Constantineau, and these seem to be associated with Quebec. Since you mention it being a "French" colony, it is very possible that could account for the name. Perhaps a French -Canadian trapper?
French Canadian names are tricky for phonetic issues.. my kids name is Dolphay.. but that came from Dauphinais.
edit-
I'll agree that, as spelled, it CAN be Italian. Looking at the circumstance and location.. my bet is that the correct spelling is probably something else.
edit 2- I looked for the records that you might be concerned with, and found...
http://ftp.rootsweb.com/pub/usgenweb/mo/...
Nearly EVERY person in this list has French names.

This is what www.ancestry.com has to say about the name.
Constantino Name Meaning and History
Italian and Portuguese: from the medieval personal name Constantino, from Latin Constantinus (see Constantine).
Hope this helps.

Last name origin & meaning:

Italian and Portuguese: from the medieval personal name Constantino, from Latin Constantinus (see Constantine).

Constantino is Italian. I've known several.