The makers of the popular European ride-sharing app BlaBlaCar have raised $100 million in venture funding, one of the largest venture investments in a French startup on record.

Index Ventures led the Series C investment in ComutoSA, the Paris-based company behind BlaBlaCar, joined by earlier backers Accel Partners, French fund ISAI and Lead Edge Capital. Executives and investors declined to disclose the valuation.

Venture...