Born on 13 July 1913 in Kijow. His grandfather participated in the January Uprising for which he was sent into exile. When Polish troops occupied Kijow, Olszewski s two elder brothers joined the Polish Army. He himself arrived to Poland with parents in 1922. He graduated from the Technical Railway School in Warsaw, and joined the Engineer Cadet Officers
School in Modlin, from which he graduated in1932. During his service in 4 Engineer Battalion in Torun, he got interested in aviation. In 1935, after an air training in the Pomeranian Flying Club, he became a tourist pilot. In 1936 he was assigned to military aviation, to a training flight of 4 Air Wing in Torun. In September 1939 he was ferrying training aircraft (by air), and then he was flying in a staff flight (commanded by F/Lt Henryk Wirszyllo). He flew six reconnaissance sorties. He went to Romania, France, and finally he got to Great Britain, where at first he flew in an anti-aircraft artillery cooperation unit (2 AACU). On 8 September 1941, after conversion training in 61 OTU at Heston, he was assigned to No. 315
(Polish) Fighter Squadron City of Deblin. He served there for a year, and then he was posted to No. 603 RAF Fighter Squadron, (he flew there through the whole March 1942). Later he was assigned to No. 54, and then to No. 64
RAF Fighter Squadrons on the Faeroe Islands. In July 1942 he returned to No. 315 Squadron. From there he was posted to 53 OTU as a head of final fighter training (in January 1944), and in April 1944 to 61 OTU. He commanded a flight in No. 302 (Polish) Fighter Squadron City of Poznan(from September 1944 till October 1944), and from October 1944 a flight in No. 308 (Polish) Fighter Squadron City of Krakow.On 24 February 1945, when F/Lt Zygmunt Bienkowski was shot down in an air combat over the Netherlands, Ignacy Olszewski was appointed as the commander of No. 302 Squadron (on 25 February). On 14 March 1945 he himself was shot down over the Netherlands. Thanks to help of the resistance movement he managed to avoid German captivity, and return to his unit. From 1 July 1945 till 30 July 1946 he was the commander of No. 308 Squadron. During his air service he flew in 160 combat sorties, on 1 January 1945 he shot down a Fw 190 aircraft. He returned to Poland in November 1946, and was working in the Gdansk Restoration Department. He was also an instructor in a flying club. In 1947 he was forbidden to fly. In 1950 he graduated from the Architecture Faculty in the Gdansk Polytechnic. In 1957 he returned to military aviation. He was the organizer and the first head of the Flight Safety Department in the Air Force HQ. He was promoted to group captain. In 1968 he retired from air force, and started to work in the Pharmaceutical Industry Design Office, where he worked till 1978. He designed many commemorative plates for Polish airmen, among others: in the St. John s Cathedral, and the Polish Armed Forces Field Cathedral in Warsaw,
the Air Chapel, and in the School of Eaglets in Deblin. He was also one of the founders of the Polish Air Force Association (in 1992).

His decorations include:
Silver Cross of Virtuti Militari War Order No. 11063 (awarded on 27 May 1946), Cross of Valour and two bars, andDistinguished Flying Cross.