I'll go with Lee Won-jung who played Baek Hee-seop in My Perfect Stranger. He was by far the best thing about that show and did a stellar job in some really tough scenes.

Rookie as in "inexperienced actor" or rookie as in "first drama"???

I'm choosing the latter definition, of course, and so my answer is unequivocally and definitively: Park Kang-hyun.

Despite having years of experience on the stage, he's got exactly one drama to his name, HeartBeat. I know I'm not alone in hoping he becomes just as common a sight on our screens as he has been in front of live audiences.

I'm over here trying to find someone to pick who is not the obvious, but who am I kidding? It's Lee Chae-min for me.

I loved both of our boys in Crash Course in Romance, but he had a bigger role and impressed me a bit more. His character was vaguely frustrating in See You in My 19th Life, but I still enjoyed watching him glowering from the sidelines, and be extra punchable in the 1st life flashbacks. Excited to see him in his next project!

Are we talking of rookies in 2023 or in recent years.

Well there's being a breakout of some i particular enjoy, either by a personal watch or due praise by beanies who loved their performance (like Lee Shi-woo in Paper Moon).

The rookie actor going for is Kang Sang-joon. Reason - his role in O'PENing's One Reason We Can't Meet. Why? His performance here forced me to remember where I must have seen have but definitely did not take cognizance of him - Bora! Deborah. Perhaps because his stint in Bora was quite minimal, I wasn't able to notice him shine. With the opportunity the drama special afforded him, shine he did without wasting airtime. He was inexplicably grounded beside UEE I thought he was one actor who had many acting portfolios but no leading role. Alas! He has just Bora and another drama special in 2021. Massive respects from me. He's a rookie actor I'm looking forward to seeing what he does in the near future.

There are a lot of a cute puppies, I mean aspiring rookies!

Kim Do Hoon : I liked him in Here's My Plan, Today's Webtoon, The Law Cafe and now in Moving. He acted pretty different roles.

Kim Moo Joon : I liked him in Love All Play. I'm curious to see more of Crown Prince's scenes in My Dearest.

Choo Young Woo : I'm not sure if he's still a rookie, he was the lead in Once Upon A Small Town, but was the second lead in Oasis. I really liked him School 2021, he was way better than the ML.

Lee Shin Young : He was one of the cute duckling in Crash Landing on You and since I liked to watch him in different roles in Awaken, How to Buy a Friend, Dr Romantic 3 and The Rookie.

But I agree with the other names : Lee Min-jae, Kim Jae-won, Lee Jong-won, and Lee Shi-woo, Kim Woo-seok, Tang Joon, etc...

Kim Yoon Woo. I have never seen him in anything before, but his performance in My Dearest has been excellent so far.

Choi Hyun Wook. There are many others I am looking forward to but if I had to pick one, it’s this guy. But I fear if he doesn’t grow taller then this might not end as well as I want it for him (sad reality in the entertainment business, esp if it’s Korea). He will be my new generation hyun bin or that’s the hope.

Picking one?! Ahhh so hard.

I will go with my most recent choice: Kim Yoon Woo. He has only been in TWO dramas before My Dearest.

He's already slaying me with his emotional acting (and heartbreaking vocals).

For one of my fave actors that been under my radar, I picked Lee Jin-hyuk from the Kpop boyband Up10tion (Find Me in Your Memory, Dear M (only released in Japan as I knew), Check Out the Event, Why Her) because that was he born 13 days before my birthday (LJH: June 8, 1996; mine: June 20, 1996). I knew he was such good performances in all of my fave Kdramas and also he did well in singing as well. Since he was now an idol-actor, I hope he had many projects to come so I braced myself for his upcoming Kdramas as well as his first film.

I realize there ate far and away more rookie actors ro choose from than actresses. None of them have wowed me to the point that they are my favorite, but all these choices by recappers and beanies seem good to me.

Lee Won Jung.

Choi Hyun Wook (25-21, Racket Boys, Weak Hero Class 1, DP 2, Twinkling Watermelon).

I have watched him in 25-21 and in Weak Hero Class 1 and I think he is really charismatic. He stole many scenes in those shows.

I have other rookie actors I like, but Choi Hyun Wook is the first one that has gone through my head.

I agree @DaebakGrits that I can't picture Tang Jun-sang in a full-fledged romance. Some actors just don't give off the vibe of romantic leading men, and Tang Jun-sang is one of them.

I pick one of Moon Sang-min, Lee Min-jae, or Kim Jae-won who all steal the scene in whatever show they're in and are heart-fluttering.

Kim Yoon-woo (Ryang-eum) from MY DEAREST.

Lee Jung Ha. He totally stole my heart in Moving.

It's Moon Hyunwook and Moon Sangmin for me. I know you said one, but I picked two. So there. lol

Hard to pick between Lee Chae Min and Lee Min Jae. They were both truly adorable and the one thing that kept me going with CCIR

I really like ths rookie actor that played Ryang Eum in My Dearest, Kim Yoon Woo. He is the only one I remember atm he also played the houng version of the ML in Delightfully Deceitful. He is really good for a rookie. More so with My Dearest since he is with the ML as much as the FL. He does not seem that green and can hold his own.

I agree with @DaebakGrits while Tang Joon-sang might have already starred in leading roles, his performances were always amazing! I’m curious to know why he hasn’t been in any new dramas lately? Is he doing military service? Both RACKET BOYS and MOVE TO HEAVEN had good reviews. Hope to see more of him!

That said, Kim Kang-hoon takes my vote! He outacted Song Joong-ki in REBORN RICH and held his own against Lee Sung-min, their scenes together were riveting!

I will go with the actor playing teenager Hee-seob from My Perfect Stranger. The actor stole the show and made me enjoy only the scenes he was in.

@missvictrix should watch Arthdal so she can join the Yangcha fanclub for Ki Do Hoon. Except she also shouldn't watch Arthdal because nobody should watch Arthdal lmao.
He has no lines and wears a mask the whole time and yet still manages to steal the entire second half of that trashfire LOL.

(But- Mianhae, Yangcha, neither Magic Horse nor you could get me to watch the Upcoming Show that Also Doesn't Exist.)

Lots of good mentions on this thread, plenty of whom are already on my list, but mostly I just want Choi Hyun Wook to stop picking stories that I'm allergic to, WHY.

I simply can't pick one. I'm grateful there is so much talent. May they and their talented female counterparts all grace our screens in the years to come (instead of the untalented actors that are sometimes favored) and also get the great scripts and production teams they deserve. A prayer thrown out to the drama lords.

My pick is Hwang Min-Hyun. I've only seen him in My Lovely Liar, and while there's still room for development for him, I found him sincere, and sometimes simple, but not superficial. I rarely use the word "endearing" for a male character, but his portrayal of Kim Do Ha in MLL made his character very endearing to me.

Baek Hyun Sung in Miraculous Brother. That kids has raw talent. He can capture the innocence of Kang San's char and act so well complimenting Jung Woo. His range is quite a fit. Will definitely watch him for sure

I'm going to pick Noh Sang-Hyun. I've only seen him in 2 dramas, but wow did he stand out! Curtain Call and Pachinko. He hasn't done too many dramas/movies. I'm not sure if he would count as a Rookie or just an actor that hasn't had much success being cast--he has already past that 30 year old mark (1990). Maybe, he has another career in a different part of entertainment....but, I really did like seeing him on screen.

I must be part of the 1% who were not interested in Crash Course IR so I'm not inclined towards the two rookies from that drama. There are actually a lot of names in the comments which I don't recognise so I don't know about the freshest rookies but I will second:
-Choi Hyunwook (great screen presence, memorable in all his roles)
-Tan Joonsang (he is THE Yoon HaeKang after all!!!)
-Kim Dohoon (it's impressive how you can see his character in Moving is holding back a lot of emotions under that restrained demeanour)
-Lee Won-jung (stole the show in My Perfect Stranger, he showed a lot of range within that one role)

My pick for best rookie actor is the underrated Ahn Ji-ho (of Nobody Knows and Move To Heaven). I thought he gave a very mature performance for such a young actor and I loved the chemistry between him and Kim Seo-hyung in the drama.

Interestingly, Ahn Ji-ho is also starring in the upcoming "BTS Universe"-inspired drama Youth along with my other favorite rookie discovery, Kim Yoon-woo (of My Dearest). Can't wait to see those two together on-screen!

I wish photos were added of each rookie, cuz I honestly don’t think I have watched enough dramas lately to know those rookies, to me Lee Do Hyun is still a rookie, cu I just heard of him this year, and out of dramas I watched I don’t really remember young actors that well

Kim Jae-Won: King the Land (Ro-woon, airline steward)
Kim Yoon-Woo: My Dearest (Ryang-Eum, singer)

Tang Joon-Sang is phenomenal and had a leading role in a drama "Move to Heaven" (excellent movie "A Melody to Remember" as a child actor)

Ki do hoon!

Park Solomon. I only saw him in REVENGE FOR OTHERS. He portrayal of the empathetic and sensible guy with doe-like eyes warmed me up to him quickly, then bam! His violent vigilante was brutal, hard to watch. That duality won me over.

I'm sitting here, wondering how Choi Hyun Wook has skipped everybody's mind. He literally started his career in 2019 and has been a necessary part of every drama he has been in. Seriously, from Twenty-five Twenty-one to D.P.2, what's not to like?

Of course, some other are on my radar: I really hope Tang Joon Sang will leave romance roles and take on characters; he has the flair for it. Ki Do Hoon in Once Again 😍 and Moon Sang Min