The Special Issue “Operator Theory and Harmonic Analysis in Armenia – celebrating the 80th anniversary of the Academy of Sciences of Armenia” has been published in the Journal of Mathematical Sciences (https://link.springer.com/journal/10958/volumes-and-issues/280-1). This Special Issue is a collection of selected papers from the Workshop OTHA Spring 2023 held from 18 to 22 April 2023 in Yerevan. There were no officially appointed Guest Editors. But we are very glad that the President of the Academy of Sciences of Armenia Prof. Ashot Saghyan, Academician, Doctor of Sciences, supported this issue and provided his greeting to the participants of the issue. The Academy of Sciences of Armenia was established on November 10, 1943, and 23 well-known scientists were elected as founding academicians, including M. Abegyan, the Alikhanyan brothers, R. Acharyan, Av. Isahakyan, V. Hambartsumyan, the Orbeli brothers and others. The first president of the Academy of Sciences was an outstanding scientist, historian, and orientalist Iosif Orbeli. Since then, many great names of researchers from Armenia have been inscribed in the annals of world science thanks to their discoveries and achievements, among them there are many mathematicians who have taken their rightful place among the outstanding scientists - see Editorial https://doi.org/10.1007/s10958-023-06583-y by Alexey Karapetyants and Editorial https://doi.org/10.1007/s10958-023-06584-x by Ashot Saghyan.