This article presents the life and work of Professor Mieczysław Konopacki, a Polish physician, freemason, social and political activist. Mieczysław Konopacki was born in 1880 in Wieluń, a town with almost 800 years of history. After passing his secondary school-leaving examinations in 1899, he began his studies at the University of Warsaw. Thanks to his diligence and commitment to research, in 1903, he received the degree of candidate of all-natural sciences at the Imperial Warsaw University. In the same year, he was arrested by the Russian authorities for his involvement in developing education in the Polish countryside and forced to move to Cracow, where he began his studies at the Faculty of Medicine of the Jagiellonian University. In 1907, he married and moved to Lviv with his wife, who was also an embryologist. There, the couple began working at the Histology Department. Also, there, in 1911, Mieczysław Konopacki obtained his doctor’s degree in medicine. He was an extremely hard-working and broad-minded man. He was a member of many associations and international scholar organizations. He took an active part in many congresses and symposia. In independent Poland, Professor Konopacki was involved in the organization of science. He tried to compensate for the many years of neglect caused by the policy of the partitioners. In 1933 Professor Konopacki was elected Vice President of the Warsaw Branch of the Young Men’s Christian Association. Complementing the social activity of Professor Konopacki was his activity in the Grand National Lodge of Poland. He died in Warsaw on September 25, 1939, fatally struck by shrapnel from a German bullet.