This research is motivated by the phenomenon of the use of two local languages, namely the Rampi and Uma languages, in the daily interactions of the people of Mamu Village, Pipikoro District, Sigi Regency. The use of these two languages indicates language contact that allows code-mixing to occur in community communication. This research aims to describe the forms of code-mixing from Uma into Rampi and to identify the factors that cause code-mixing in the interactions of the people of Mamu Village. This research employs a descriptive qualitative approach. The data sources consist of utterances produced by the people of Mamu Village, collected through observation, interviews, participant observation, non-participant observation, recording, and note-taking techniques. The data were analyzed through the stages of transcription, identification, classification, and interpretation based on sociolinguistic studies and code-mixing theory. The results show that the forms of code-mixing found include the insertion of words, phrases, and clauses, with word insertion from Uma into Rampi being the most dominant form. The factors causing code-mixing include speaker-related factors, language habits, social closeness between speakers, the bilingual environment, and the desire to clarify the intended meaning of an utterance. This phenomenon demonstrates the close social relationship between Uma and Rampi speakers and reflects the dynamics of language contact in the daily life of the people of Mamu Village. Thus, code-mixing functions not only as a means of communication but also reflects the social and cultural identity of the local community. ABSTRAK Penelitian ini dilatarbelakangi oleh fenomena penggunaan dua bahasa daerah, yaitu bahasa Rampi dan bahasa Uma, dalam interaksi sehari-hari masyarakat Desa Mamu, Kecamatan Pipikoro, Kabupaten Sigi. Penggunaan kedua bahasa tersebut menunjukkan adanya kontak bahasa yang memungkinkan terjadinya campur kode dalam komunikasi masyarakat. Penelitian ini bertujuan untuk mendeskripsikan bentuk campur kode bahasa Uma terhadap bahasa Rampi serta mengidentifikasi faktor-faktor yang menyebabkan terjadinya campur kode dalam interaksi masyarakat Desa Mamu. Penelitian ini menggunakan pendekatan deskriptif kualitatif. Sumber data penelitian berupa tuturan masyarakat Desa Mamu yang diperoleh melalui observasi, wawancara, teknik simak libat cakap, simak bebas libat cakap, teknik rekam, dan teknik catat. Data dianalisis melalui tahap transkripsi, identifikasi, klasifikasi, dan interpretasi berdasarkan kajian sosiolinguistik dan teori campur kode. Hasil penelitian menunjukkan bahwa bentuk campur kode yang ditemukan meliputi penyisipan kata, frasa, dan klausa, dengan bentuk yang paling dominan berupa penyisipan kata bahasa Uma ke dalam tuturan bahasa Rampi. Faktor penyebab campur kode meliputi faktor penutur, kebiasaan berbahasa, kedekatan sosial antarpembicara, lingkungan bilingual, dan keinginan memperjelas maksud tuturan. Fenomena tersebut menunjukkan adanya hubungan sosial yang erat antara penutur bahasa Uma dan bahasa Rampi serta mencerminkan dinamika kontak bahasa dalam kehidupan masyarakat Desa Mamu. Dengan demikian, campur kode tidak hanya berperan sebagai sarana komunikasi, tetapi juga mencerminkan identitas sosial dan budaya masyarakat setempat.