TheoryDesk Jr (or TheoryDesk Junior) is a line of computers manufactured by Theorysonic. Released in October 1986, it was originally aimed at the education market but was later made available as a cheaper mass market alternative to the TheoryDesk E2. The TheoryDesk Jr was pulled from retail on April 30, 1993, and was sold exclusively to educational institutions thereafter. It was discontinued on September 20, 1997, and replaced by TheoryDesk Mini.

The design of the TheoryDesk Jr closely resembles the TheoryDesk E2. Compared to the E2, TheoryDesk Jr's colors are the opposite and slightly smaller. Unlike the E2, the TheoryDesk Jr has less memory and storage and lacks a carrying handle.

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