Mother of three Yujnovich, who has been based in Calgary as an executive vice president of Shell's oil sands operations since 2014, will assume both Andrew Smith's executive vice president Australia & New Zealand position and take the role of country chair.
Before 2014 that Yujnovich held frontline and management roles in mining across three continents.
She joined Rio Tinto in 1996 after obtaining an engineering degree from UWA. At Rio Tinto she held roles including company president in Brazil and CEO of the Iron Ore Company of Canada.
Smith said Shell's Australian business had been "transformed" since he returned from London in 2010, and said the supermajor would play a major role in global energy markets for "decades to come".
"Consistent with Shell's global strategy to simplify its portfolio and only invest in the most compelling projects we went about reshaping the business," Smith said.
"We took the difficult decisions to sell the refining business, including the profitable retail division, moved our upstream business into operatorship - through the acquisition of QGC and progress of the Prelude floating LNG project - and saw first gas flow from Gorgon LNG," he said.
"Today Shell's Australian portfolio is a globally significant LNG export business that will continue to make a tangible contribution to Australia's economy. As an Australian I am proud the business I have led is a massive part of Shell's world-class investment case.
"I am very pleased to welcome Zoe back to Australia, her leadership in Shell's Canadian business has been instrumental to improving both the economic and environmental performance of this complex business."
Yujnovich said Smith left Shell's business in Australia in a "strong position, as we continue to build a viable export business while meeting the demands of local customers".
"I'm particularly excited about continuing to leverage the strong businesses we have in Australia and getting even closer to our customers as their needs and our industry continue to evolve," she said.
"Andrew has been a strong voice in consistently calling for the kind of regulatory reform that makes Australia a country that can attract investment in job creating projects - particularly outside the prosperous capitals in regional areas.
"I look forward to building on his legacy both by running Shell safely and efficiently, but also by being an active voice in the national debate."
Yujnovich is also Shell Canada vice president operations, having overseen the supermajor's sell-off of $1.3 billion in Canadian oil and gas assets, part of a $30 billion global divestment program.
Shell had already pulled back from some capital commitments in western Canada, and delayed a decision on whether to build an LNG export terminal in British Columbia, citing global energy challenges.
In October 2015 it halted its Carmon Creek oil sands project in northern Alberta due to lack of infrastructure to move crude to market, while Shell more recently divested Tourmaline as it didn't fit into the supermajor's near-term development plans.
Shell still holds nearly 650,000 net acres in the Montney and Duvernay shale plays and is still a major oil sands producer in northern Alberta.
It gave up its Arctic exploration permits to clear the way for Canada's third national marine protected area last June, after abandoning its Arctic search for oil in 2015 having failed to find enough crude despite spending about $7 billion on exploration off Alaskan waters.
Shell also flagged that it would take a $4.1 billion hit for pulling out of the treacherous Chukchi Sea, where icebergs can be as large as New York's Manhattan Island.
Its Australian options are seen to be headed in a more positive direction, as BG Group's LNG portfolio including Queensland Curtis LNG was a big reason for Shell's $US50 billion acquisition of its UK rival.
Shell has already announced that its Arrow CSG project won't be a standalone development, and is looking at options of tying it into existing infrastructure.
Across the Tasman Sea, Shell called on JP Morgan last August to offload its $A1 billion-plus portfolio of oil exploration and production assets in New Zealand, after the firm sold Shell's Maui gas pipeline in 2015 to First State Investments for $NZ335 million.
In 2014, Vitol paid $US2.6 billion for Shell's Australian refinery and petrol stations.