Bortkiewicz was born in St. Petersburg, Imperial Russia (today Russia) where he graduated in law in 1890.

In 1898 he published a book about the Poisson distribution, titled *The Law of Small Numbers*. In this book he first noted that events with low frequency in a large population follow a Poisson distribution even when the probabilities of the events varied. It was that book that made the Prussian cavalry horse-kick data famous. The data give the number of soldiers killed by being kicked by a horse each year in each of 14 cavalry corps over a 20-year period. Bortkiewicz showed that those numbers follow a Poisson distribution. The book also examined data on child-suicides. Some historians of mathematics have argued that the Poisson distribution should have been named the "Bortkiewicz distribution."

Bortkiewicz died in Berlin, Germany.

- Biographical sketch on the web site of the University of St. Andrews (in Scotland)