Language functions as a medium of communication that enables individuals to interact within their social environment. Proper and correct Indonesian refers to the use of the language in accordance with prevailing social norms and linguistic rules. However, the use of Indonesian in newspapers often demonstrates deviations from these norms. This study aims to describe the grammatical errors found at the sentence level in opinion articles published in Harian Analisa. The research employs a qualitative descriptive method, with data obtained from selected opinion texts in the newspaper. The data were analyzed using descriptive analysis techniques based on Purwandari’s linguistic theory. The findings reveal seven main types of sentence errors: (1) completeness, (2) parallelism, (3) conciseness, (4) coherence, (5) variation, (6) diction accuracy, and (7) spelling accuracy. The study concludes that the Indonesian language used in Harian Analisa opinions still requires improvement in syntactic and lexical accuracy. These findings are expected to serve as a reference for enhancing public awareness of proper and correct Indonesian language use in written media.