irony of fate; twist of fate
Used when events turn out in a way that is contrary to what was expected, often with a sense of cruel or poetic justice.
It's an irony of fate that he had an accident.
By a twist of fate, she was fired on her own birthday.
Compound of 運命 (fate) + の (possessive particle) + 皮肉 (irony). The phrase is a straightforward combination of its parts.