Activist investor Carl Icahn has a new Silicon Valley target— eBay Inc.

After his recent runs at Apple Inc., Netflix Inc. and Dell Inc., Mr. Icahn wants eBay to carve off payments unit PayPal. He has acquired a stake equivalent to 0.82% of eBay's shares and has nominated two people to its board, eBay said Wednesday in reporting fourth-quarter results.

EBay said it would fight Mr. Icahn's effort. "We believe that our collection of assets drive more growth and more success together, than apart," said Chief Executive John Donahoe in an interview Wednesday. "The eBay marketplace accelerates PayPal's success; the eBay marketplace provides data that makes PayPal smarter." Mr. Donahoe said he had spoken with Mr. Icahn last week.

Mr. Icahn wasn't available for comment, his assistant said.

PayPal, which allows people and businesses to exchange money digitally, is considered by many to be eBay's crown jewel. The unit is on a pace to eclipse the company's namesake online marketplace in terms of sales.