Abstract: This research aims to describe the code choide of female santri in the religiosity domain. This research was conducted at Assalaam Islamic Modern Boarding School and Islam Al-Mukmin Boarding School of Ngruki, Sukoharjo Regency. Its data were speech between female santri and female santri, speech between female santri and female teachers (ustazah)/male teachers (ustaz) in the religiosity domains. They were collected through observation, recording, listening, note-taking, and in-depth interview. The result of the research find out that there was a tendency that Indonesian code was chosen as the main media of communication while the other speech codes were used for interethnic communication. In religiosity domain, the codes used were Indonesian, code switching from Indonesian to Arabic, and English. Indonesiaan is the most code used by people in the religiosity domain.Keywords: code choice, santri, religiosity domain.Abstrak: Penelitian ini bertujuan untuk mendeskripsikan pilihan kode santri wanita dalam ranah keagaman. Penelitian ini mengambil lokasi di Pesantren Modern Islam Assalaam dan Pesantren Islam Al-Mukmin Ngruki di Kabupaten Sukoharjo. Data yang terkumpul dalam penelitian ini merupakan tuturan santri dan santri, santri dan ustazah/ustaz dalam domain keagamaan di lingkungan Pesantren Modern Islam Assalaam dan Pesantren Islam Al-Mukmin Ngruki. Teknik pengumpulan data yaitu teknik observasi, rekam, simak, catat, dan wawancara mendalam. Hasil penelitian menunjukkan bahwa ranah keagamaan ditemukan pola pilihan kode yaitu bahasa Indonesia (BI), alih kode dari bahasa Indonesia ke dalam bahasa Arab, bahasa Inggris. Kode tutur yang paling sering digunakan dalam ranah keagamaan yaitu bahasa Indonesia.Kata kunci: pilihan kode, santri, ranah keagamaan.