Movies or dramas about forbidden love / in love with someone they can't have?

These are a few that I've watched. Since you didn't mention the nature of the forbidden love, I will explain how I find it forbidden for each drama I recommend!

1. Bring it on Ghost - kdrama (because she's a ghost and he's human) - naive romance

2. Jugglers - kdrama: office romance - company policy

3. Just You - twdrama - same reason as number 2

4. Love in the Moonlight - kdrama - firstly because he's the crown prince and she's a slave; secondly because he thinks she's a boy and the third reason I can't tell you, because I would spoil it for you

4. Coffee Prince - kdrama - he thinks she's a boy

5. Because this is my first life - kdrama - they can't fall in love for each other in order to live and share the same house.

6. My Teacher - jmovie - student/teacher romance

7. The Princess' Man - kdrama - Romeo and Juliet type of romance

✔️ house of Flying Daggers

✔️ Werewolf Boy 

✔️ It's Okay It's Love 

✔️ Splish Splash Love 

✔️ Flower Boy Ramen Shop

✔️ Queen  In Hyun's Man

✔️ Queen of the Ring 

✔️ Witch's Romance (2014)

✔️ My Girlfriend is a Gumiho

✔️ Lavendar (18+) 

Forbidden loves feels like taboo type romance, so i keep thinking incest or student-teacher or affairs. And in this type of relationship it is never cute in an way, cause they always end up so angsty. But i guess there are some you can check out:

• Biscuit teacher and star candy (romcom)  - student/teacher romance
• Kill me heal me (romcom with melo) - patient/doctor romance
• Shut up flower boy band (romcom)-  student/teacher romance
• My Girl (romcom) - FL is acting as ML's fake cousin
• My little bride (romcom | movie) - underage marriage plus student/teacher
• Marmalade boy (romcom) - step-sibling romance. The taiwanese version was bad, but there is a japanese live action recently which I havent seen yet
• Sassy Go Go (romcom) - They became step sibling toward the end
• sprout (coming of age) - leads are in a relationship with other peoplebut they are attracted to each other.
• autumn in my heart (melodrama) - kinda sibling relationship with tragic end
• My love eundong (melodrama) - FL is married when they meet again as adults
• Big (romcom fantasy) - student/teacher plus the teacher is his brothers fiancee. But this drama was disappointing
• Triple (romcom) - underage romance plus stepsibling relationship. This was a little disppointing but i loved all the male characters
• +1 My teacher - student/teacher

How about semi-forbidden love (semi-taboo), where the 2 leads could have been related through marriage but a partner of one character dies?

• What Planet are You from (romcom) - ML is the fiancee of FL's twin that died 
• Falling for innocence (romcom) - ML is the recipient of FL's fiancee heart
• My Lovely Girl - same scenario from above but this was disappointing

but unto love that cannot be, i feel like these are the ones that are all about star-crossed lovers where the parent generation has bad blood and it spills over the main leads . And usually they are all angsty too, though some have cute meoments between the leads:

• Ashes of Love (wuxia with a cute start) - the ML's parents is the reason of FL's mother tragedy
• Moonshine and Valentine (romcom wuxia) - the FL is like a sacrificial lamb for ML'slife/power as a fox tail creature every single lifetime of the human FL.
• Goblin (fantasy romcom) - FL will be the reason for ML to finally meet his death after thousand years
• marry me or not - FL is mortal frenemy of ML's sister
• + princess man - star crossed lovers

• Something in the Rain - age gap / not-related-by-blood family / parental opposition
• In Time With You - best friends; the ML likes the FL from the beginning, but due to certain circumstances he declares at the outset of their friendship that he'll never have feelings for her; they're never both single at the same time
• Love Lost in Times - a prince and a sorceress, the royal family is not allowed to fraternize with sorcerers
• The Princess Wei Young - the ML is a prince of an empire and the FL is a princess of a kingdom that was overtaken by the empire / the emperor forbids them from being together
• The Imperial Doctress - the FL marries the ML's half brother and opponent in a struggle for the throne
• W - the ML is the main character in a manhwa (so he's a fictional character) written by the FL's father, who gave him a tragic backstory and never planned a happy ending for him - essentially sentencing him to eternally pursue an outcome that can never be achieved
• On the Way to the Airport - the leads are both married to other people
• Pinocchio - not-related-by-blood family / family opposition

and +1 for:

• Love in the Moonlight / Moonlight Drawn by Clouds
• Coffee Prince
• The Princess' Man
• Come and Hug Me

Sparrow (that happens to several characters).

 Stevie70:

✔️ house of Flying Daggers

✔️ Werewolf Boy 

✔️ It's Okay It's Love 

✔️ Splish Splash Love 

✔️ Flower Boy Ramen Shop

✔️ Queen  In Hyun's Man

✔️ Queen of the Ring 

✔️ Witch's Romance (2014)

✔️ My Girlfriend is a Gumiho

✔️ Lavendar (18+) 

I am at ep 3 of It is ok,that is love and I don`t see where it can be forbidden ?I mean if we ignore her  problems regarding intimacy it is all ok?Don`t spoil me ,just tell me if there is reason to be forbidden .

 Yuki Akisa:

I am at ep 3 of It is ok,that is love and I don`t see where it can be forbidden ?I mean if we ignore her  problems regarding intimacy it is all ok?Don`t spoil me ,just tell me if there is reason to be forbidden .

She is dating her patient and he has a mental illness which you will find in later episodes