Upvote:3
You have few possibilities:
The most used option, the ferry: Ancona to Igoumenitsa or Patras, twice a day. I do not know if Ancona is too distant for you, but you should definitely check such ferries: they are frequent.
You may find also some ferries from Venice to Igoumenitsa and Patras, three times a week.
I cannot find a route from Genoa or France (no indirect routes).
Upvote:13
The go-to resource for ferries is ferrylines.com.
When I search for ferries from Italy to Greece, it lists 26 results:
We can readily see some of them are departing from the north. Specifically, there are six lines from Venezia to Greece:
You can use their search engine for yourself to look for further alternatives and information. If you feel adventurous, you can consider the ferry from Trieste to DΓΌrres, Albania, and then drive into Greece from there!