What do you call this bar? rear suspension

What a total rust protection fail. Just curious:

That's a Prime? What year? What's your location?

The name of the game is, on a weekend, pick one end (I'd start with the rear in your case), jack it up and onto safety stands, take off the wheels, remove accessible plastic panels, clean everthing, and apply rust-proofing. Fluid Film is highly recommended. I've used boiled linseed oil, just applied with brushes. Holds up good, seals/stops existing rust.

^ Solid rear axle, that's gotta be a third gen. Or second?

Report the first post (click edit button, report is there), ask mods to move.

 

That looks like one of the body braces; definitely too flimsy for a suspension component like a stabilizer.

Gen 3 has a few of those braces, as I recall, and you can find them in the drawings at parts.toyota.com.

 

It's Toyota part number:
5360547020

It's:
53605-47020 Toyota Brace sub-assy, rear suspension 5360547020.

It's the diagram part reference 53605F in the image below (lower right).
Note that Toyota has two similar parts with that diagram number.

Code:

https://static.amayama.com/schema/toyota-5360547020-1565857802024-big.jpg

Good Luck!

 

Just order one from one of the salvage yards down in Georgia USA they have hundreds of miles of Prius in that state in various junk yards and perfect condition as far as rust goes and underbody and chassis parts You could buy the whole rear section of the car and have it shipped to you for less than a few of the parts you'd buy from dealer probably just a guess but they're constantly writing me telling me what they have and showing me miles and lines of cars one of these days I'm going to take a ride down there and have a look Camry's too man it's unbelievable and they sit there for quite some time until they get crushed and all the nonsense goes on it's really wild If you go on eBay you can find the junk yards then click on their pictures and look at that mess not a house or nothing in the site just miles and miles of Toyotas it seems like big outfits