We developed Ti-Mn alloys containing 5-20％Mn (by mass) as the base composition for high-strength titanium alloys, and investigated the alloy phases and mechanical properties of their castings. X-ray diffraction analysis revealed that Ti-5-7％Mn alloys consist of α and β phases, while compositions exceeding 8％Mn exhibit a metastable β phase. Peaks corresponding to the ~ phase were observed in the 6-8％Mn alloys. The hardness of Ti–Mn alloys was consistently higher than that of Ti, with 7％of Mn alloys reaching hardness levels exceeding 500 HV due to ~-phase precipitation. Metastable β phase alloys with 10-15％Mn exhibited hardness levels of approximately 350 HV. The tensile strengths of Ti-5％Mn and 9-14％Mn alloys significantly surpassed that of Ti, with Ti-5％Mn and 10％Mn alloys exhibiting tensile strengths exceeding 800 MPa. Solid solution and precipitation strengthening, or solid solution strengthening contributed to these enhancements, respectively. Although elongation in Ti–Mn alloys was relatively low level, dimples were observed on the fracture surfaces of some compositions. Based on our findings, the base composition for developing high-strength dental titanium alloys is Ti-10-14％Mn alloys.