tl;dr: No, *Gotham* is separate, as are *iZombie* and *Lucifer*. The rest of the DC shows are all effectively in the same universe (or multiverse, to be precise). Also, note that none of these shows are considered part of any movie universe (e.g. none of them are part of the DCEU)

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In the 2014-2015 and 2015--2016 TV seasons, there's **a ton** of DC shows on the air:

* *Arrow*
* *The Flash*
* *Constantine*
* *Gotham*
* *iZombie*
* *Supergirl*
* *Legends of Tomorrow*
* *Lucifer*

The only explicitly shared universe in that group is the "Arrowverse" which includes the three shows aired on CW and produced by Greg Berlanti, Andrew Kreisberg and Marc Guggenheim: *Arrow*, *The Flash*, and *Legends of Tomorrow*.  

At [Comic Con 2014](http://io9.com/ras-al-ghul-comes-to-arrow-and-other-dc-tv-news-from-co-1611625466) it was stated that there's no shared universe among the others, as of yet:

> While we know that *Arrow* and *The Flash* will crossover a lot, it was deemed a little difficult to cross over the non-CW shows, since *Gotham*'s time period is a little uncertain. *Gotham* executive producer Bruno Heller said, "Never say never" but pointed out "If those two [*Gotham* and *Constantine*] worlds coincided, then it would work. But I'm not really sure of the chronology. Maybe *Constantine* is only five when *Gotham* takes place."

So far, *iZombie*, *Lucifer* and *Gotham* have remained separate, and their setting and tone are diverse enough that they'll probably remain that way. However, after *Constantine* was cancelled by NBC, Berlanti's team got Matt Ryan to reprise his lead role on S4E05 of *Arrow*, meaning that *Constantine* retroactively joined the Arrowverse. In addition, in S01E18 of *Supergirl* (also produced by Berlanti's company), Grant Gustin appeared as Barry Allen, also bringing *Supergirl* into the Arrowverse continuity.