The Council of Nicaea, held in 325 AD, declared that the Father, Son and Holy Spirit are of one substance (homoousios) but differ in persona (hypostasis). In other words, the three are equal yet fulfil different roles. Just as the Nicene doctrine emphasizes unity amid diversity. Kartini argued that Javanese women possess equal dignity to men, although their societal roles are often restricted by patriarchal cultural norms. This article employs a comparative historical-philosophical approach to examine how the concept of unity in diversity in Trinitarian theology parallels Kartini's views on women's equality. Kartini's thoughts reflect the biblical assertion that man and woman are created equal and will become one flesh. Equality, in this context, does not imply equal functions, but rather an equality of substance. This study offers a fresh perspective on feminist theology and historical gender studies by demonstrating how the model of unity in diversity found in theology can enhance our understanding of women’s dignity and social roles.