Konstantīns Pēkšēns (born 3 March 1859, Mazsalaca parish, Russian Empire — died 23 June 1928, Bad Kissingen, Weimar Republic) is one of the most prominent Latvian architects of all times.

Pēkšēns also sat in the councils of a number of credit institutions and banks, and acted as a spokesman for the Riga Latvian Society.

All those associates of Pēkšēns, just like Aleksandrs Vanags, August Malvess, and others who later became well known in Riga in their own right, accumulated their professional experience while working in the construction and technical office of the master.

During the golden age of Art Nouveau of the early 20th century several buildings with a fascinating abundance and variety of decorative motifs typical for this new style were designed by Pēkšēns.

The most characteristic feature of Pēkšēns creative work, is the respective reserve and deep logic of architectural forms arising out of the Art Nouveau artistic principle, namely, the beauty of a building should not depend on outside applications, but derive from a practical and utilitarian layout.

Some designs by Pēkšēns contain romanticised reminiscences of historical motifs, others stand out by a vertical compositional arrangement that became especially characteristic of Riga's Art Nouveau movement around 1910.

The most outstanding houses designed by Pēkšēns outside Riga are the District Council buildings in Ādaži and Dole, the church in Lejasciems (1895), his own summer house in Dzintari, the temporary concert hall in Jelgava built for the IV General Latvian Song Festival (1895), and Nicholas' Church of the Latvian parish in Jelgava (1904—09, demolished after World War II).