Legal certainty of property rights certificate holders regarding land encroachment by other parties. Encroachment on someone elses land can lead to legal issues, considering the existence of a Land Ownership Certificate that grants full ownership rights over the land to the certificate holder, serving as proof of land ownership and also encompassing rights, guarantees, and legal protection that must be afforded to the landowner. One of the cases the author refers to is the Supreme Court Decision number: Number 681 PK/Pdt/2019. Therefore, several objectives sought are as follows: To examine and analyze the legal certainty of the certificate holder from land encroachment by housing development actors reviewed under the UUPA (Basic Agrarian Law) and To analyze and comprehend the legal protection of the certificate holder from encroachment by other parties in case number 681 PK/Pdt/2019 reviewed under the Civil Code. The author chose a normative legal research method for this thesis to analyze legal issues by seeking accurate and valid facts about a particular event through secondary data or literature. The approach focuses on statutory law (statue approach) and case-based approach (case approach). After gathering relevant data concerning the raised issue, the researcher then conducts qualitative analysis. Based on legal certainty in the land sector, especially as regulated in the UUPA, to provide legal certainty to the certificate holder. In this case, proving that legal certainty of someone's land certificate regulated by the UUPA can serve as a guide for the Panel of Judges in making well-considered decisions. All elements of Unlawful Acts have been fulfilled, and the Defendants are considered to have committed Unlawful Acts according to Article 1365 of the Civil Code because the purpose of land registration itself is to provide legal certainty to the land certificate holder consistent with legal practice, as provided to Mr. Liem Sian Tjie as the holder of the Land Ownership Certificate. Therefore, the Plaintiff can prove the physical truth of the land in this case because the certificate is well-documented. The Defendants action (PT. Surya Mitra Persada) fulfilled the elements of an unlawful act. Reference: 75 (1945-2021) Keyword : Freehold Title,Land Encroachment, Legal Protection