Study aim: To determine the effectiveness of Acceptance and Commitment Therapy (ACT) on sexual function in pregnant women. Design: This study will be a randomized controlled trial with a parallel‑group design. Participants will be randomly allocated to the two groups (1:1) using the RAND function in Excel, with allocation concealment maintained. Assessments will be conducted at baseline, post‑intervention, and two‑month follow‑up. The study will be single‑blind, with the outcome analyst blinded to group allocation. Participant blinding will not be possible due to the nature of the intervention. Settings and conduct: The study will be conducted in Torbat-e Heydariyeh, Iran. Participants will be recruited from comprehensive health centers, gynecology clinics, and midwifery counseling centers. The intervention sessions will be delivered online via the Skyroom platform. Participants/Inclusion and exclusion criteria: Inclusion criteria: Singleton pregnancy without serious medical complications Gestational age between 12 and 24 weeks at enrollment. Access to the internet and a smart device to participate in online sessions Willingness and ability to attend all intervention sessions. Absence of severe or persistent psychiatric disorders. Provision of written informed consent. Exclusion criteria: pregnancy complications, withdrawal, absence from >1 session. Intervention groups: Intervention Group: Participants will receive Acceptance and Commitment Therapy (ACT) in four weekly online group sessions of 90 minutes. Content includes acceptance of unpleasant thoughts and emotions, mindfulness exercises, cognitive defusion, self-as-context, values clarification, and committed actions. Homework will be assigned for each session. Control Group: Participants in this group will receive no psychological or online intervention. They will only receive routine prenatal care and standard educational services provided at health‑care centers. Main outcome variables: Sexual function of pregnant women measured using the total score of the Female Sexual Function Index (FSFI).