As far as the "Largest" Star ... visible from Earth ... Thus, in Sun's relative context ... there are Trillions ... though only few of these have been Classified ... while most, yet remain to be Classified, and Categorized.
But you can be sure, when you look up at the skies on a clear night, there are hundreds, perhaps thousands of dim Stars ... most being by far much larger, than our sun ... adorning our Earth's Night Skies.
I was thinking the Sun at first, too, but the sun is a rather small star. It appears large because it is relatively close. There are giant stars that can be seen from earth, but some of them are millions of light years away.
Sirius was the first star that popped into my mind-- it's the brightest visible from Earth...but then immediately I thought, well, there might be stars bigger but farther, so they would appear less bright than Sirius.
Then I wondered, 'how do we know how big a star is?' Science is cool, insn't it? No deadends--one question leads to a network of other questions...
Endlessly fascinating. Well, for dweeby nerd girls like myself. I was born just a tad too early to be cool, but my neice Megan is simpatico and she's completed an elite Penn State computer science degree (her graduation ceremony was a hoot--she's short in stature anyway, and marching to place with the other (mostly boy) students receiving the same degree, she looked like a little munchkin surrounded by giants.
Ah, geek girl power. I love to see it. She ruled those boys, too. They were in awe of her mind and her ability to organize projects and find unique solutions.
Plus she's adorably cute. Okay Okay...now I've gone over the line and I'm bragging on my children; well, my brother's children as I have none of my own.
NOTE: This is from WIKI and even they admit it's outdated, but it still was the clearest I could find after a few hours of stupid sleepy useless research and I refuse to go any further, so here's my final reply:
Star name↓ Solar radii (Sun = 1)↓
VY Canis Majoris 1,800–2,100; VV Cephei A 1,600–1,900[foot 1] V838 Monocerotis 1,570 ± 400 Mu Cephei (Herschel's "Garnet Star") 1,650 WOH G64 1,540 V354 Cephei 1,520 KY Cygni 1,420–2,850 KW Sagittarii 1,460 RW Cephei 1,260–1,610 Betelgeuse (Alpha Orionis) 1,180 Antares (Alpha Scorpii) 800[foot 2] V382 Carinae 747 S Pegasi 580 W Hydrae 562 T Cephei 540 S Orionis 530 R Cassiopeiae 500 Chi Cygni 470 Alpha Herculis (Ras Algethi) 460 Rho Cassiopeiae 450 119 Tauri ("Ruby Star") 450 Mira A (Omicron Ceti) 400 V509 Cassiopeiae 400–900 S Doradus 100–380 U Orionis 370±96 R Doradus 370 HR Carinae 350 R Leonis 350 Nu Aquilae 350 V337 Carinae 350 The Pistol Star 340 S Coronae Borealis 340 V381 Cephei 327 Pi Puppis (Ahadi) 290 Delta Lyrae 275 Psi Aurigae 271 Alpha Draconis (Thuban) 265 CW Leonis 250 Cygnus OB2-12 244 Omicron Canis Majoris 231 Gamma Cygni (Sadir) 225 Deneb (Alpha Cygni) 220 La Superba (Y Canum Venaticorum) 215
It sounded like such a simple question. But there's so much complication. Like much of life: all chaos once you scratch the surface. That's why most of us don't scratch.
Being part cat, after living with the Fuzzy Ones and, realizing their vast superiority over the Opposable Thumbed Ones, I've aspired and meditated and studied and mind-melded until I've grown claws that can't help but scratch surfaces.
Visible from Earth. Visible with or without telescope? With infrared telescope? Do giant massive red dead stars that keep accumulating more and more mass till they collapse or explode or something count or only living stars that are relatively stable?
Sigh. Mew. Nap time. No wonder cats sleep so much. We burn up calories in endless loops of musing that may keep us amused and others bemused but serve no purpose other than to make nap time all the more desireable and dreams more interesting. If I only had a real brain, I'd have the perfect temperment to be a theoretical physicist.