Ao3:
Deliverance by Zeds_Dead_Reader (Zeds_Dead)- I'm still reading this so I'm not sure if this is canon to the storyline but it has the basic plot down.
Tomorrowland by Satre_Proxy (ongoing)- The reader is from our world and is teleported into the anime. It's well written and an enjoyable read. It ends off till either season 1-2 I forgot
Silver Soul by oi_levi- This is post canon (after season 4) still reading this but I like it a lot
Death's Door by SongsOfApollo (ongoing)- one of my favs. The reader is a doctor and is told to help out the Survey Corps. It ends off on season 1 or around there.
This doesn't usually happen by DesertRose07 (ongoing)- another one of my favorites. It ends off on the end of season 2.
Mystery by YavenaVerman (ongoing)- THE BEST FIC I'VE READ!! It's starting a bit of season 4 already, the OC is badass and it's such a great slow burn.
To Honesty and Comeuppance (Text Version and Podfic Version) by Tolstoy Ackerman (JuicyDangler) (ongoing)- I haven't read this but it looks like a great fic that follows through with canon
Wattpad:
Fable by AOTSMUT I think this is post canon I'm not sure but this gets recced a lot and I read a little bit of it and have enjoyed it so far.
𝐑𝐈𝐕𝐀𝐋 | Levi Ackerman by 2005Jade (ongoing)- Ends around season 2. one of my favs on wattpad the author writes so beautifully and the slow burn between the oc and Levi is great
Surviving Soldier by ecstasy_of_silver (ongoing)- still reading, ends on either season 3 or 4
Reign Of Blood by mudbloodmama- read a few chaps and it looks interesting. There's a sequel with season 4
This one isn't romance:
Wings [Levi Daughter] by Y_Allen- still readin, there's a little bit of romance with someone else in season 4 but it's very slight. I loved seeing Levi's character growth into being a great dad for her.
YOU ARE READING
My Levi/reader and OC recommendations
RandomMost are on ao3 and wattpad Just posting some Levi fanfics I liked