Yes. The Quran sets a severe punishment for those who accuse chaste people without four witnesses (24:4), and curses those who slander believing women who never thought of evil (24:23). It is a major sin.
Kuma waɗanda ke jĩfar mãtã masu kãmun kai, sa'an nan kuma ba su jẽ da shaidu huɗu ba to, ku yi musu bũlãla, bũlãla tamãnin, kuma kada ku karɓi wata shaida tãsu, har abada. Waɗancan su ne fãsiƙai.
Lalle ne waɗannan da suke jĩfar mãtã mãsu kãmun kai gãfilai mũminai, an la'ane su, a cikin dũniya da Lãhira, kuma sunãda azãba mai girma.
This is general information, not a fatwa. For your own situation, ask a qualified scholar.
Questions about halal and haram
Is falsely accusing someone of immorality haram?
Yes. The Quran sets a severe punishment for those who accuse chaste people without four witnesses (24:4), and curses those who slander believing women who never thought of evil (24:23). It is a major sin.