The 1978 Amco Cup was the 5th edition of the NSWRFL Midweek Knockout Cup, a NSWRFL-organised national club Rugby League tournament between the leading clubs and representative teams from the NSWRFL, the BRL, the CRL, the QRL, the NZRL, Western Australia and the Northern Territory. A total of 38 teams from across Australia and New Zealand played 37 matches in a straight knock-out format, with the matches being held midweek during the premiership season.