* Q1 sales 980 mln euros vs analyst consensus for 977 mln
* Q1 adj EBIT 20.3 mln euros vs consensus for 22.5 mln
* 2017 guidance confirmed
* More than 20 mln active customers at end of Q1 (Adds details)
BERLIN, May 9 (Reuters) - Zalando, Europe's biggest pure online fashion retailer, saw first-quarter sales grow 23 percent, supported by a marketing campaign featuring U.S. actor James Franco aimed at attracting more male customers.
Founded in Berlin in 2008, Zalando has expanded rapidly and now delivers 1,500 brands in 15 countries, with women accounting for the bulk of its sales. However, as growth has slowed, it is pushing into new categories like menswear and sports gear.
Zalando, which already reported preliminary results last month, said sales came in at 980 million euros ($1.07 billion), while adjusted earnings before interest and taxation (EBIT) was flat at 20.3 million, broadly in line with analysts forecasts.
The 23 percent rise compares with a growth rate of 24 percent in the same quarter a year ago and a rate of 26 percent in the fourth quarter of 2016.
Sales rose 17 percent in Zalando's core Germany, Austria and Switzerland region and 28 percent in its other, newer markets in Europe. It reiterated a forecast for 2017 sales growth of 20 to 25 percent and an EBIT margin of 5 to 6 percent.
British rival ASOS, which trades at a premium to Zalando as it is seen as better insulated from Amazon's push into fashion, last month lifted its annual sales forecast to between 30 and 35 percent, but stuck to its profit outlook.
Zalando said it exceeded 20 million active customers at the end of the first quarter, compared to some 14 million at ASOS, which targets a narrower market of fashion-conscious twenty-somethings.
$1 = 0.9156 euros Reporting by Emma Thomasson; Editing by Maria Sheahan