Knox was recently assistant to Richard Gough at Livingston

Knox, assistant to the current Scotland manager Walter Smith at Rangers and Everton, will also be responsible for all the other national youth teams.

Smith hailed the news as "an excellent appointment" for Scotland.

"His experience and knowledge will be of considerable benefit to the young talent which is coming through the ranks today," he added.

"The SFA is placing increasing emphasis on developing our age-group international squads, and having Archie here will allow us to build on the considerable progress that has already been made."

Scottish Football Association chief executive David Taylor added: "Archie commands great respect from the players and other coaches.

"He has had a successful career and his ideas, enthusiasm, and organisational knowledge will be of great benefit to the work of the Scottish FA."

Knox starts work immediately and will travel to Poland with the under-19 group for the finals of the Uefa under-19 Championship.

The first competitive fixture for the under-21 team is against Slovenia on 16 August.