By Uday Sampath Kumar

July 8 (Reuters) - Instacart named Facebook Inc app head Fidji Simo as its chief executive officer on Thursday, adding big tech expertise ahead of an expected stock market listing by the U.S. grocery delivery firm.

French-born Simo will replace co-founder Apoorva Mehta, who will take on the role of executive chairman and still be involved in day-to-day activities, Instacart said.

Simo's appointment comes at a crucial time for the nine-year-old startup, as expectations build for its public debut following a year in which its business grew four-fold due to the pandemic-driven surge in online grocery shopping.

"We're here to build a long-term business over the next few decades," Simo, who takes the helm early next month, told Reuters.

"Facebook's IPO was just a moment in time and what happened afterward was really what mattered, which is delivering a lot of value to people and that is really what I am going to be focused on."

Reuters reported in March that Instacart was considering going public through a direct listing, just a few days after a funding round valued the company at $39 billion.

Mehta declined to comment on which path the company was considering to go public, but said a key reason in choosing Simo was her experience at Facebook during the social media giant's transition to a public company in 2012.

"I'm excited about Fidgi's experience as a public market executive in a company that has seen so much growth," he said.

Simo said she plans to use her experience to build out Instacart's advertising business, aiming to boost revenue from consumer-packaged goods companies promoting their products on its app.

The focus on alternate revenue paths comes as Instacart faces new challenges, including a likely slowdown in delivery demand as people return to stores.

(Reporting by Uday Sampath in Bengaluru; Editing by Aditya Soni)