Simple. Full studio discographies you own? But 4-5+ albums only.
GH or any other releases don't matter & don't count.

Rihanna

Gaga

Beyonce (No DC, does that count?)

I think just Nicki and Little Mix.

I own Bey and Ye's 2010s releases.

EDIT: Wait, I don't own anyone's discography with those rules lmfao.

Ciara
Lady Gaga

Beyonce counts, but the other 3 don't, cause they have only a few albums.

Gaga (it's kinda 4)
...yeah
Just miss 2 Britney albums (Britney + ITZ) and by Rihanna I miss the first 3 and most likely never getting them
6 Kylie albums out of 12

I think just Taylor Swift's. I almost have Arcade Fire and Beyonce's full discography but there are a couple bonus tracks/random tracks that I don't have for both of them.

Edit: Maybe not even Taylor since I don't have those Christmas tracks she did

Britney.
Miley.
Beyonce.
Xtina.

Katy too but she only has three albums.

Edited, Gaga technically has 4 albums. no?

Ciara
Beyoncé
Selena Gomez
Selena (EMI Albums only)
I only own 5 Kylie albums.

Bey

Brandy, Bey, Pink, Rihanna, Ariana, & Adele.
All of Selena/Selena & the scene except kiss and tell

Gaga (TF, TFM, BTW, ARTPOP and Unreleased )

Rihanna

Mariah

TFM isn't an album it's just an EP

----
Avril (LG, UMS, TBDT, GL, AL)
Enrique(Escape, 7, Insomniac, Euphoria, Sex and Love )

Television
The Velvet Underground
Rihanna
Taylor Swift
Radiohead
Arcade Fire

Lady Gaga, Rihanna, Beyonce, Ke$ha, Britney.

oop. I think I have Taylor's full discography too.
Christmas tracks don't matter. That's why I said "studio albums".


EP is not a studio album technically, but sure. It's long enough to be an album.

According to Billboard and UK charts it's too long for an EP