The ring appears to be a ruby in the middle of diamonds that surround the gem, making the piece of jewelry look like a flower.
"full bloom," Perry said in the post.
Only Bloom's left eye appeared in the photo, with Perry looking teary-eyed. Shiny red balloons adorned the background.
Bloom's caption simply said, "Lifetimes."
The celebrity pair first started dating in 2016, when news of their romance went public after attending a Golden Globes after-party together, according to Hollywood Life.
Perry was previously married to comedian Russell Brand, while Bloom was previously married to model Miranda Kerr.