This is a controversial topic and there is no one way to make a “correct” separation between generations of k-pop groups (actually it is questionable if there are generations after all, personally I prefer talking about “eras” or “phases”). There are some definite periods of k-pop music, but the transitions are flowing and it is often hard to decide whether a group should belong to a phase defined by the year of debut alone or the style of music and theme of an entire era. Some people argue there are at least 5 generations as of now, others count only 3. Most fans accept that there are 3-4 generations and we will use that concept here, too. Please note that this is a personal view on things and does not claim to be the “right way” or only way to see it.

Upcoming The group is going to debut soon, group name, members and some promotional images have been announced.
Cancelled A group that was about to debut soon but for some reason the debut got delayed indefinitely or the whole project was cancelled.
Active The group is considered to be still active, that means they are promoting or doing stage performances, attend TV shows and show clear signs of activity as a group. Their latest release should be no longer than 2 years ago (regardless of country or format).
Hiatus A group that does not count as active due to longer inactivity or lack of releases but has not officially disbanded is counted as “on hiatus”. Some groups are declared to be on hiatus officially by their labels but often they simply stop releasing and promoting and sort of “disappear”.
Disbanded A group that is declared having disbanded by the label or group members.
Long Hiatus In some cases a group on very long hiatus should be considered being disbanded even if group members say otherwise. Especially when many group members actively pursue different careers like acting or solo careers, it sometimes can be safe to assume that the original group formation will never again release anything. Especially if the members have already grown older (25+). After School is a good example for this.
Solo Singer These are iindividual performers, often former group members, that have started a solo career in the music scene. There is no safe indicator here for their level of activity, some of them have not released new material in years.

Generation 1 (1996–2003)

First generation of K-Pop began with the birth of the idol industry after the debut of H.O.T. in 1996 and follows the early years of K-pop with fresh, feminine girl groups debuting, and includes idol groups debuting from 1996 to 2003. An extension of First Generation called Generation 1.5 is sometimes separated, including groups from 2000 to 2003.

1994 Cool
1996 B.B. Seo Chan Whee
1997 Baby V.O.X Diva ECO Han's Band S.E.S Tutti Park Ji Yoon Um Jung Hwa Yangpa
1998 Circle Fin.K.L. KYT/Koyote Kim Hyun-Jung
1999 O-24 As One Cleo See U T.T.MA Tashanni Baek Ji-young Lee Jung Hyun
2000 Chakra Papaya BoA Lee Soo Young Wax
2001 Jewelry KISS M.I.L.K Nazcar Sugar Toya Jang Nara Dana Yoon Mirae
2002 Isak N Jiyeon Luv Shinvi
2003 Big Mama Bubble Sisters Bada Chae Yeon Eugene Gummy Lee Hyori Lexy Ok Ju-hyeon
Upcoming Cancelled Active Hiatus Disbanded Long Hiatus Solo Artist

Generation 2 (2004–2009)

Second Generation evolved in the early 2000s and saw K-pop spreading throughout Asia and beginning to be introduced to the West, especially with the slow rise of social media, saw a diversification of concepts and genres. It includes idol groups that debuted from 2004 to 2009.

2004 7 Princess Shyne Younha Sunday
2005 The Grace (CSJH) Gavy NJ I-13 LADY LPG Orange Sorea Band Ivy Jessi
2006 2NB Brown Eyed Girls Girl Friends Kirots SeeYa Kan Mi-youn Zhang Liyin
2007 Baby Vox Re.V Black Pearl Cats / The Reds 2nd Kara Girl's Generation (SNSD) Sunny Hill Swan Wonder Girls Iconiq J-Min Seo Inyeong / Elly Son Dambi ZIA
2008 Dambi Davichi Miss $ Wink IU Joo Navi Solbu / Kwon Jian
2009 2NE1 4Minute 4Tomorrow 7Size After School Brand New Day f(x) HAM / Heart & Mind JQT Lady Collection Rainbow Secret Sweet Revenge T-ara Urban Zakapa ALi DIA Gilme Hong Jinyeong Kim Sori NS Yoon-G Park Bom Sohyun Song Jieun Tymee (E.Via)
Upcoming Cancelled Active Hiatus Disbanded Long Hiatus Solo Artist

Generation 2.5 (2010–2012)

An extension of Second Generation called Generation 2.5 is typically described as the transitional period between Generations 2 and 3. This period saw a growth in the idol industry, beginning to see the start of the oversaturation of K-pop, making the industry much more competitive. This era includes idol groups debuting from 2010 to 2012.

2010 B-Dolls BeBe Mignon Black List Chocolate Coed School D.Heaven EVAS G.Story Girl's Day GP Basic Miss A Nine Muses Orange Caramel Sistar Vanilla Lucy VNT G.NA Gain Gil Hakmi Hyuna Jessica Ora Park Boram Shoo Soya Stephanie (Kim Bokyung)
2011 2Boram Apink April Kiss Baby Soul + Yoo Ji Ah Bella Black Eye Blady Brave Girls C-REAL Chi Chi ChoColat CLINAH Coin Jackson Dal★Shabet EI-YO Elizabeth F-ve Dolls HaraSora INY Leader'S New.F.O Piggy Dolls Pinkdolls RaNia (BP RaNia) SpinEL Stellar Swing Girls Swincle Wind Hold Venus Women Power Blue Berry Fat Cat Geum Dan Bi Kahi Rottyful Sky / Hanul (†)
2012 15& 2winD& 84LY Akdong Musician AOA AS 1 BBde Girls BIKINY / GIRLFRIEND Black Queen ➜ Hey Girls BT Swing Crayon Pop D-Unit D.Q Dazzling RED E2RE EvoL Exid Fiestar FlaShe Gangkiz GLAM Goddess Hello Venus High Lady ➜ High.D Hey Girls (Black Queen) ILIPS Jevice Lay.T LXIA Melody Day Mystic White NEP P.O.P CON ➜ Queen B'z Pandora Puretty Ruby (The) She'z Six Bomb SKARF Spica Sunny Days Tahiti The Barberettes The SeeYa Tinus Tiny-G Two X VIVID Ailee Anda(miro) Baek A Yeon BEN Juniel Lee Hi Stephanie
Upcoming Cancelled Active Hiatus Disbanded Long Hiatus Solo Artist

Generation 3 (2013–present)

K-pop saw another boost with the Third Generation that grew in the digital age with the influence of social media and resulted in the globalization of the genre. This era also saw a growth in survival programs that pushed for more competition, and includes idol groups that primarily debuted in 2013 onward. Considering typical contracts to last seven years, that generation could be followed by another one from 2020 on.

2013 2Eyes 2Yoon A-DEAN AGirls AltheA BESTie Bom & Hi BP Pop Delight GI / Global Icon Heart Rabbit Girls K-Girls Heart Rabbit Girls Hint (Turan) Ladies' Code Live High Lush (The) Mamamoo NC.A N*White Pascol Peach Girl Peemine Pungdeng-E Purplay Queen B’Z S - The One Switch Berry The Gloss Tint Tren-D Turan➜ I+#NT WA$$UP
42 total, 22 disbanded, 1 hiatus. 1 cancelled
CL Heyne Joo A Kim Bo-hyeong Shin Ji-hun Sunmi U Sung Eun Z.Hera
2014 1PS 4L/Four Ladies 4Ten A-Daily A-Fati Aila A.I.N A.KOR ANDS Badkiz -> Hot Place BarbieD (Kiwi Band M) Bay.B Bebop Bella4 Berry Good Billion Bob Girls Bubble X D.Holic GirlHood Hi Suhyun Hot Place (Badkiz) Kiss&Cry Laboum Lip Service Lodia Lovelyz Luluz Melody Day Minx → Dreamcatcher M.O.A. N*White Ouigee Poot Poot Purfles Rainbow Blaxx Red Velvet Road Girls Rosemary Scarlet Smile.G Sonamoo Spica.S Step Girl Switch Tarine The Unnies Topic Vetty-L Vidan Wings Ye-A Year 7 Class 1
53 total, 39 disbanded, 1 hiatus
Alice Vicious (Livii) Alice White Cheetah esNa Gong Min Young HA:TFELT Heize Hyomin J-Min Jiyeon Jun Jyunseong Kim Na-young Kissum Megan Lee Nicole Park Bo-ram Park So-jin Shannon Suran
2015 10X10 4Some ACE A.H.H.A A-plus April As 1 Asha A.Some ATT AweSome Baby BaBa/Pureum BabyBoo Bambino Blackswan Bellroseya CLC Cupid DIA GFriend Girls Girls H2L Honey Friends I.C.E Icia (SIDA) Jjarimongttang Laysha LoveUs MyB Oh My Girl Playback Pocket Girls PPL Rubber Soul SUS4 The Ark Tweety Twice Unicorn UNIZ Verry Vividiva Wanna.B ZzBest
44 total, 28 disbanded, 3 hiatus
Baek Yerin Elsie Heeca Hwang In Sun Jina_U Jucy KissN Miwoo Park Ji-min Ryu Sera Shin Zisu Soyumi Yeseul Yezi
2016 A.De Awesome Day Black Pink Blity Bloomy BolBBalgan4 (BOL 4) Bulldok C.I.V.A CocoSori Dorothy Gugudan Heymiss Hi.D Highteen Hash Tag Holics Holly Queen I.B.I I.O.I Matilda Mercury Mixx Momoland Moxie/Magsi New-A Queendom Real Girls Project Oahsis/SeeArt Sol-T Sunny Girls Unnies Various Wable WJSN (Cosmic Girls)
34 total, 17 disbanded, 4 hiatus
Aisle Cosmic Girl Dalbodre Dalsoobin Grace Han Seung Yeon Hyolyn Jenyer JooHee Kim Ju-na Kinie.K Mintty/Mint Monika Moon Hyuna Nada Seol.A Tiffany
2017 20 (Duo) 1NB 2Wenty's 4X ABRY Amor Apple.B A-seed Awesome BeBe6 Berry Chu Blah Blah Bl.eX.Y Busters BONUSbaby Burny Girls (Duo) Cashcoma (Duo) Chic Angel Chloris Day Day Dreamcatcher Elris Favorite Fanxy Red (ACRUSH) G-reyish GeeGu/Gate 9 Girls' Alert Girls Next Door Good Day H2L Hash Tag Heart Hi Cutie HINT H.U.B K.A.R.D Limesoda Lipbubble Marmello My Darling O My Jewel Pit A Pat P.O.P Pristin Ramisu Rose Quartz S2 S2U S.I.S S.E.T (s3t) Sunny Play The Two Of Us Triple H VIVA Walwari Weki Meki XoX Yellow Bee ZZBae
59 total, 2 cancelled, 19 disbanded
CherryBerry Choyoon Chungha Faver Hayana Honey Apple Hur Young Ji I (Cha Yun-ji) Im Bo-reum/Lily Ina Jung HyeRin Kang Si-ra Kasper Kimi Kim Sohee Kisses Kriesha Chu Minzy MiSO Saay Seohyun Soma Soyou Suzy YuSeol
2018 (G)I-dle 12DAL (Duo) 2TS / 30대 걸그룹 (Duo) A.B.O. ALiKE AiRiSU AQUA A Train To Autumn AZM B Girls Bbeum Berry Good HEART HEART* Black Mamba Blue Fox BONUSbaby BBURECTOR Camila Celeb Five Cherry In Top CST D:amant (Duo) Destiny DPOP Friends Dreamnote Fanatics First Bite Flossom Flow Sister Fromis 9 GBB Girlkind Geupsik-Dan ➜ D-Crunch GWSN (Girls in the Park) Honey Popcorn ii IZ*ONE Jelly Girl Khan Kitten Girls LOONA Maywish My Darling Musky Nature Neonpunch Oahsis/SeeArt PIERCE PinkFantasy PRISM Purple Red In Ear Rose Finger Saturday ShaFLA ShaSha Sio.Sijak Sugar Powder (Prom.Unit) Sugar Tint Sun&Moon (Duo) TeensEL Tropical Uni.T Vitamin We Girls WJMK/Wuju Meki Wish Girls YJIG YPDA Zzangdalla
70 total, 1 pending, 3 cancelled, 5 disbanded, 1 hiatus
Alice Ashley A-Yeon Carla Gracie HeeRa J.Mee Kang Hye-yeon Katie Lua Mia Migyo Minseo Minty Moon Seulgi Ryu Seojin Sooyoung Sori Tia Yel Yubin Yoo YerY
2019 3YE 4CARAT ALLS-Girls ANS API ARIAZ AZM Black Bunny BVNDIT Cherry Bullet CoCo CSVC Deluxe Everglow Fanatics Fly With Me G-(i)Kon Girl Crush Gloss Grow.B High Color (Duo) High School Ho1iday ➜ A Hot Place ii (Duo) I LUV ITZY K-Tigers Zero Label Up Lalary LUSTY Mayqueen Melody Pink Midnight PEACE PlayM Girls/Favegirls Purplebeck Q6IX/Retrose Refiners Rendezvous Rocket Punch Rockit Girl SKYGIRLS Swalla/A-Mix The Pink Lady U.A UHSN Venus White Day Z-Girls Hwa Jeong Jayeon maRe Sohlhee Somi
Upcoming Cancelled Active Hiatus Disbanded Long Hiatus Solo Artist