Embryo implantation, a crucial step in human reproduction, is tightly controlled by estrogen and progesterone (P 4 ) via estrogen receptor alpha and progesterone receptor (PGR), respectively. Here, we report that N 6 -methyladenosine (m 6 A), the most abundant mRNA modification in eukaryotes, plays an essential role in embryo implantation through the maintenance of P 4  signaling. Conditional deletion of methyltransferase-like 3 ( Mettl3 ), encoding the m 6 A writer METTL3, in the female reproductive tract using a Cre mouse line with Pgr promoter ( Pgr-Cre ) resulted in complete implantation failure due to pre-implantation embryo loss and defective uterine receptivity. Moreover, the uterus of Mettl3 null mice failed to respond to artificial decidualization. We further found that Mettl3 deletion was accompanied by a marked decrease in PGR protein expression. Mechanistically, we found that Pgr mRNA is a direct target for METTL3-mediated m 6 A modification. A luciferase assay revealed that the m 6 A modification in the 5′ untranslated region (5′-UTR) of Pgr mRNA enhances PGR protein translation efficiency in a YTHDF1-dependent manner. Finally, we demonstrated that METTL3 is required for human endometrial stromal cell decidualization in vitro and that the METTL3-PGR axis is conserved between mice and humans. In summary, this study provides evidence that METTL3 is essential for normal P 4 signaling during embryo implantation via m 6 A-mediated translation control of Pgr mRNA.