|Full name||Frederick Windsor Warren|
|Date of birth||23 December 1907|
|Place of birth||Cardiff, Wales|
|Date of death||1986|
|1936–1939||Heart of Midlothian||62||(29)|
|* Senior club appearances and goals counted for the domestic league only.
Warren began his career at his home town club Cardiff City, spending time as understudy to George McLachlan before becoming a more regular first team player. In January 1930, he was sold to Division One side Middlesbrough for a fee of £8,000, in a transfer that also involved Joe Hillier and Jack Jennings. After six years with Middlesbrough, Warren joined Heart of Midlothian, where he later became the clubs first Welsh international. He remained at Tynecastle until the outbreak of World War II, returning to South Wales to work for Barry Town.
Warren made his debut for Wales on 2 February 1929, scoring in a 2–1 win over Ireland in the 1929 British Home Championship. Four months later, during the summer of 1929 Warren was selected for the Football Association of Wales tour of Canada but these matches were not classed as international cap matches. His Cardiff City teammates Len Davies, Fred Keenor and Walter Robbins were also selected for the tour. During his career, he earned 6 caps for Wales over a period of nine years, scoring three times with all three being scored in matches against Ireland at the Racecourse Ground.
- Results list Wales' goal tally first.
|1.||2 February 1929||Racecourse Ground, Wrexham, Wales||Ireland||2–1||1929 British Home Championship|
|2.||22 April 1931||Racecourse Ground, Wrexham, Wales||Ireland||3–2||1931 British Home Championship|
|3.||17 March 1937||Racecourse Ground, Wrexham, Wales||Ireland||4–1||1937 British Home Championship|
- "Search 1984 to 2006 – Birth, Marriage and Death indexes". Findmypast.com. Retrieved 2009-06-16.
- "1934-1944". Heart of Midlothian F.C. Retrieved 2010-03-20.
- "Wales 2-1 Ireland". Welsh Football Data Archive. Retrieved 2010-03-20.
- "British "FA XI" tours". rsssf.com. Retrieved 2010-03-19.