Mary Ann Belliveau has spent 25 years doing one of the least glamorous and most valuable jobs in advertising: walking into the offices of the biggest brands in America and convincing them that a platform they don't take seriously deserves real money. She did it for Google. She did it for Twitter. At Reddit, she did it at a scale that turned a punchline into a public company.

Now she's doing it for Snap, in the one part of the business the company has admitted, in writing, to its own shareholders, that it hasn't figured out.

Every ad platform has two sales businesses. One is the self-serve machine, where small and midsize advertisers plug in a credit card and an algorithm does the rest. The other is large customer sales: the Fortune 500 brands, the holding company agencies, the upfront negotiations, the quarterly business reviews where someone from a CPG giant asks why their brand lift study looks worse than Meta's.

The first business scales with engineering. The second scales with people. It is relationship work, organization work, and above all translation work: turning a platform's product into something a chief marketing officer can defend to a CFO.

That second business is Belliveau's entire career. Snap hired her in July 2025 as president of North America Sales, and her title now reads President of Americas, leading the Large Customer Solutions business. When she arrived, she said she was "thrilled to join the Snap team and dive into Snap's North America business."

She was diving into the deep end.

Before most of today's ad tech executives had business cards, Belliveau spent more than a decade at Google, where she was a founding member of the Industry Development and Marketing team. Her career listings show her as Industry Director for Healthcare, one of the most regulated and cautious categories any ad seller can take on.

The detail that matters most from that era is not a title. Her official bios credit her with "playing a key role in building the company's sales and business leadership bench" and with hiring and mentoring many of the people who went on to run Google's business.

That is a specific kind of legacy. Plenty of sales executives hit numbers. Far fewer build the machine that keeps hitting them after they leave. It is a theme that will come up again.

At Twitter, Belliveau rose to Managing Director of Large Customer Sales, and her career history shows her leading national sales across health and wellness, automotive and financial services. She built Twitter's health and wellness advertising practice.

Think about what that meant. Pharma, insurers, banks and carmakers are the most risk-averse buyers in advertising. They have legal departments that read creative line by line and compliance teams that treat social media the way most people treat a stranger's unattended bag. Getting those categories comfortable on an open, chaotic, real-time platform is the hardest version of the social sales job.

She took the hardest version.

Belliveau joined Reddit in 2019, and the timing tells you everything about the bet Reddit was making. At the time, Reddit was still widely treated by brand marketers as the internet's comment section: huge, passionate, and a little terrifying.

Reddit COO Jen Wong explained the hire in plain terms. Belliveau had already done the work of explaining a new kind of platform to marketers. "She's been through that cycle before and can help us shape that."

She climbed fast. Her Reddit history runs from Senior Director of East Coast Brand Partnerships to head of Large Customer Sales to Vice President of Large Customer Sales for North America, working with Fortune 500 companies and their agencies. By 2024 she was on stage at CES, talking about the future of community-based advertising and user privacy, which is Reddit's entire commercial pitch in one sentence.

And the numbers moved. During her tenure, Reddit grew revenue from under $100 million to over $1 billion in five years, and went public in 2024. No single executive gets sole credit for a curve like that. Product, ad tech, data licensing and a much-improved self-serve business all did their part. But the big-brand dollars that turned Reddit from a curiosity into a line item came through her organization.

LinkedIn farewell posts are usually greeting cards. The ones that piled up when Belliveau left Reddit read more like performance reviews, and unusually specific ones.

One former Reddit colleague wrote: "It takes a really special leader to be operational, strategic, exceptional at identifying talent & building an amazing culture. You exemplify world class leadership. You built an incredible org with unprecedented revenue growth."

Another credited her with "building the rev org into the growth engine it is now," pointing to "the incredible hires you made and culture you built."

Others went personal. One called her "the most human leader." Another described "a humble and caring leader and mentor" whose door was genuinely open.

Notice what the praise is about. Not the rolodex. Not the client dinners. The org chart. Colleagues credit her with building a sales organization, hiring the right people, and creating a place those people wanted to stay. That is the Google bench story again, a decade later and at a different company.

It is also exactly the skill set Snap needs.

Snap's ad sales leadership has been a revolving door. In 2022, chief business officer Jeremi Gorman and VP of sales Peter Naylor left for Netflix to build the streamer's ad business. Snap spent the next stretch rebuilding. It brought in Microsoft's Rob Wilk as president of Americas in 2023; he lasted roughly six months before heading to Yahoo. Meta veteran Patrick Harris held the Americas title after that.

Then came Belliveau.

Ajit Mohan, Snap's chief business officer at the time, said she brought "sharp instincts, deep client expertise, and a strong track record of building and scaling teams." Wall Street noticed too: a Citizens JMP analyst flagged the leadership change as a possible source of "potential turmoil" while keeping a buy rating on the stock. That is analyst-speak for: good hire, hard seat.

Snap has been refreshingly blunt about what she inherited.

In its Q1 2026 investor letter, Snap said large advertisers in North America remained a headwind to advertising growth. It said it was "not satisfied with that outcome." It called the recovery among bigger North American advertisers "early and uneven," and explained why: those customers plan on quarterly and semiannual cycles, so revenue lags behind improvements in performance and measurement.

Meanwhile, the rest of Snap's ad business was humming. Small and midsize businesses made up more than 30% of global ad revenue and were the company's biggest ad growth driver for the seventh straight quarter. The self-serve machine works. The big-brand machine is the one that needed a mechanic.

Snap's own 10-Q shows the shape of it.

North America, Q1 2026: roughly 2% growth.

North America, Q2 2026: roughly 12.5% growth, to $904.9 million.

North America, first half: $1.73 billion, up about 7.5%.

Europe, first half: $669 million, up about 40%.

Here's the part the Belliveau bio should lead with, because it is hers: North America growth jumped from about 2% to about 12.5% in a single quarter, and Q2 was her fourth full quarter in the job. Snap also reported 2026 North America upfront commitments up about 10%, which is agencies putting money down in advance. Upfront dollars are the purest measure of big-brand confidence there is, and they went up on her watch.

One quarter is not a trend. But it is the first number that points the right way, and it came from the business she was hired to fix.

On September 8, Snap named Ronan Harris, its EMEA president and the man behind Europe's 40%, as Chief Commercial Officer, running global advertising sales and go-to-market. Mohan, who hired Belliveau, is leaving after nearly four years.

That changes the story around her. The executive with the fastest-growing region now runs everything, and the implicit corporate thesis is that his playbook scales. Belliveau runs more than half the company's revenue, in the most competitive ad market on earth, against Meta, Google, TikTok and Amazon on their home turf.

Europe growing 40% off a smaller base is impressive. North America re-accelerating off a base nearly three times the size is harder, and that is the work on Belliveau's desk.

Strip it down and her career is one repeated assignment: take a platform big brands underestimate, and build the organization that changes their minds. Google in its early sales days. Twitter in the categories that feared social. Reddit when marketers still thought of it as a place to avoid.

Snap is the same assignment with bigger stakes. Nearly a billion users, a generation of consumers brands cannot reach anywhere else, and a large-advertiser business the company itself describes as behind. The colleagues who worked for her say she builds teams that outlast her. Wong said she'd been through the cycle before. Mohan said she scales teams. The Q2 numbers say something may already be working.

What her résumé cannot promise is that Snap's measurement and product give her enough to sell. Snap's own letter says big advertisers are waiting for measurement to catch up with performance. Culture builds the sales team. It does not fix attribution.

But if anyone has shown she can hold a big-brand sales organization together long enough for the product to catch up, it's the executive who has now done it three times. The next four quarters decide whether Snap becomes the fourth.