Johannes Widmann (c. 1460 – after 1498) was a German mathematician. The + and - symbols first appeared in print in his book Mercantile Arithmetic or Behende und hüpsche Rechenung auff allen Kauffmanschafft published in Leipzig in 1489 in reference to surpluses and deficits in business problems.
Widman published Behende und hübsche Rechenung auff allen Kauffmanschafft (German; i.e. Nimble and neat calculation in all trades), his work making use of the signs, in Leipzig in 1489. Further editions were published in Pforzheim, Hagenau, and Augsburg. Handwritten entries in a surviving collection show that after earning his "Magister" Widman announced holding lectures on e.g. calculating on the lines of a calculating board and on algebra. There is evidence that the lecture on algebra actually took place, making it the first known university lecture on this topic.
Around 1495 Widmann published the Latin writings Algorithmus integrorum cum probis annexis, Algorithmus linealis, Algorithmus minutiarum phisicarum, Algorithmus minutiarum vulgarium, .Regula falsi apud philosophantes augmenti et decrementi appellata und Tractatus proportionum plusquam aureus