Sir Ralph Smith Cusack was chairman of the Midland Great Western Railway (MGWR) of Ireland for forty years from 1865 to 1905.

He was educated at Trinity College, Dublin, graduating BA in 1845 and MA in 1849.v[1] Cusack was appointed to the board of MGWR in 1858, the company being in some turmoil at this time.

[2] Cusack accepted the chairmanship of the MGWR in 1865 following the reluctant two-day incumbency of William Maunsell, the company at that time incurring losses.

[4] Cusack finally retired as Chairman in 1904 after about 40 years aged 84, leaving the Company in a relatively good financial position though receipts were declining.

Shepherd describes Cusack's style as "although autocratic, he was fair-minded and generally liked by all ranks".