What Is The Great Attractor? I've heard that there is something called the Great Attractor which seems to have some kind of gravitational influence on objects in the Universe.  Is this some kind of theoretical notion posited in order to help answer a question in Astronomy, or is there an actual object which is greatly attracting?

Or is this an obsolete notion?
No; it's real - observations of the movement of galaxies indicate that there is an unusual concentration of mass (probably not a massive "object" of course, but totalling as much as tens of thousands of galaxies) in a place around 200 million lightyears from our galaxy.

It's hard to study since the view in that direction happens to be blocked by our own galaxy, but given that it has been studied for decades, it seems unlikely that the phenomenon turns out to be based on some sort of methodical error.