Kayla Jean Mueller (14 Agustus 1988–6 Februari 2015) adalah seorang aktivis hak asasi manusia dan pekerja bantuan kemanusiaan Amerika asal Prescott, Arizona. Ia ditangkap pada Agustus 2013 di Aleppo, Suriah, setelah meninggalkan rumah sakit Doctors Without Borders. Media mengabarkan bahwa pekerja bantuan Amerika berusia 26 tahun ditangkap oleh Negara Islam Irak dan Syam (NIIS) tanpa menyebutkan namanya, atas permintaan keluarga. Penangkapan dan kematiannya dilaporkan setelah konfirmasi kematiannya.
James Gordon Meek (2015-08-14). "ISIS Leader Abu Bakr Al-Baghdadi Sexually Abused American Hostage Kayla Mueller, Officials Say". Washington DC: ABC News. Diakses tanggal 2015-08-14. The information about al-Baghdadi's extraordinary direct role in the captivity and physical abuse of Kayla Mueller was drawn from, among many sources, the U.S. debriefings of at least least two Yezedi teenage girls, ages 16 and 18, held as sex slaves in the Sayyaf compound as well as from the interrogation of Abu Sayyaf's wife Umm Sayyaf, who was captured in the U.S. raid, the officials told ABC News.