Mladen Koščak, Croatian footballer (d. 1997)
Mladen Košćak (16 October 1936 – 3 August 1997) was a Croatian footballer. Born in Zagreb, Košćak joined the youth academy of local side Dinamo Zagreb, with whom he spent his entire career. He started playing at full professional level in the 1955–56 season. Košćak soon established himself as a first-team regular and was instrumental in Dinamo's 1957–58 Yugoslav First League title.
Internationally, he was capped 4 times for the Yugoslavia national football team and was member of the national squad which won the silver medal at the 1956 Summer Olympics in Melbourne. Although he was considered a huge talent, his career was hampered by a serious injury and he effectively stopped playing by 1960, appearing in only a single match in his last three years with the club before retiring in 1963.