Slavoljub Eduard Penkala was a Croatian engineer and inventor who held over seventy patents. Slavoljub Penkala background was in chemistry, however, he is best known as the inventor of the first mechanical pencil first named the "automatic pencil", which he invented in 1906. Penkala started a factory called Penkala-Mostero for the manufacturing of his pens and pencils.

Other inventions Slavoljub Penkala was noted for was the first solid-ink fountain pen in 1907, and the first Croatian two-seat airplane in 1909. He also patented a hot water bottle, detergent, a rail-car brake, and a anode battery. One of his more controversial inventions was a tonic medicine called "Radium Vinovica" that was supposed to cure rheumatism.

Slavoljub Penkala was born in Liptowsky St. Mikulaš (now Slovakia) in 1871 and died in 1922 in Zagreb of pneumonia at the age of 51.