SYDNEY, Sept 13 (Reuters) - Stakeshop Pty Ltd, an online stock broker backed by tech investment giant Tiger Global, said on Monday it will launch a A$3 ($2) brokerage service in Australia, the country's cheapest.

The launch is a direct challenge to No. 1 lender Commonwealth Bank of Australia's subsidiary CommSec, the country's largest online and mobile broker, and other large competitors that have dominated the local market for years.

"I don't think there's been material change in the industry since brokerage went electronic in the late '90s and early 2000s," said Matt Leibowitz, Stakeshop's Sydney-based founder and chief executive. "So I think 25 years on, this is a big moment."

Operating as Stake since 2017, the company is known among a growing number of investors in Australia and New Zealand primarily as a commission-free retail broker for U.S.-listed stocks.

For that service, Stake's platform operates in U.S. dollars and traders are charged 0.7% on fund transfers between Australian and U.S. dollars.

It has about 360,000 customers, and trading on the app has grown 100-fold to over $1 billion per month since its launch, Leibowitz said.

The brokerage for Australian-listed stocks will be powered by Finclear, a broker-dealer 16% owned by Magellan Financial Group.

Trading in stocks listed on the local ASX Ltd exchange will be CHESS-sponsored, meaning that it will be under the person's own name, not a separate legal entity's name, as is commonly done by low-cost brokers seeking to reduce costs.

After a commission-free period until year end, Stake's commissions of A$3 a trade will compare to CommSec's tiered fees of A$10 to $29.95 for each trade worth up to A$1,000 to A$25,000, respectively.

"I think this will accelerate us towards the top," Leibowitz said. "We'll hopefully be banging down the door of number one, that would be the goal."

CommSec holds 5.4% market share in terms of the traded value of Australian stocks as of June 30, according to Commonwealth Bank's annual report. But its share of the narrower online brokerage market is estimated to be close to 40%, with the retail broker opening over 550,000 client accounts in fiscal 2021.

In June, New York-based Tiger Global led a A$40 million Series A equity-raising for Stake, which with 75 staff also operates in Britain and Brazil.

($1 = 1.3512 Australian dollars) (Reporting by Paulina Duran in Sydney; Editing by William Mallard)