Question: I was wondering how many official "*Republics*" there are in the *Star Wars* universe?

One, two, three? I know about the **Old Republic** and the **New Republic** but I was wondering if there are any more.

Can the answerer please use the Star Wars movies or *Thrawn trilogy* (I am reading the first book now) as reference because only some of my Star Wars knowledge is on the Expanded Universe.

Note: to limit confusion in answers please show your estimated time periods for each republic.

Answer: 
If you only use movies or Thrawn Trilogy, there were only two:

* Old [Galactic Republic](http://starwars.wikia.com/wiki/Old_Republic) (~25,000 years BBY - 19BBY)
* [The New Republic](http://starwars.wikia.com/wiki/New_Republic) (post-Palpatine) (4ABY-27 ABY, though one may quibble that post-28ABY Alliance should be counted)

Thrawn trilogy didn't introduce any new ones. It mentioned several worlds but none of them held an official title of Republic.

However, Later EU had other smaller republics (Ylesian Republic, Altirian Republic, Moralan republic).
For comprehension, I rather see it as Wikipedia does. "The Old Republic" ~25000 BBY, that formed into the "Galactic Republic" in 1032 BBY, [19BBY-4ABY was the Empires rise] and then the "New Republic" as it was reorganised in 4BBY and then destroyed again in 34BBY in The Force Awakens.
So, two. But people often speak of the Old Republic and mean the "Galactic Republic" phase. At least as far as I understood!