Artificial intelligence (AI) stocks have been driving the S&P 500 to incredible gains in recent years. Investors have rushed to get in on key players powering this revolution, as well as lesser-known companies that could be winners of the future. The reason for all of this excitement is simple: AI, even in its early days, has shown us it can deliver efficiency and help companies become more innovative. And all of this may lead to significant earnings growth for the developers and users of the technology.

This is a fast-moving field, but that doesn't necessarily mean all AI stocks are risky or must be watched like a pot of boiling water on your stove. In fact, one AI company in particular offers a package that cautious investors will like: a long history of earnings strength due to multiple businesses and a solid position in AI. And that's what makes this AI stock the ultimate set-it-and-forget-it buy for long-term investors. Let's check it out.

One of the world's biggest companies

The player I'm referring to is involved in many areas of technology and is among the world's biggest companies. At the same time, it got in early on AI and has emerged as one of the major players in the field. This stock to buy and hold for the long term is Microsoft (MSFT 2.55%).

Most of us are familiar with Microsoft because it's the owner of something we use every day: Microsoft 365, which includes famous products like Word and Excel. Microsoft sells these packages to individuals and businesses -- but the company's offerings go well beyond this software and apps suite.

Microsoft also generates revenue from ownership of professional networking platform LinkedIn, gaming brand Xbox, its cloud business, and more. All of this has helped the company's earnings grow over time. This track record offers Microsoft investors a certain sense of security as they can count on revenue and growth from the tech giant.

MSFT Revenue (Annual) data by YCharts

Meanwhile, the company has also become a key player in the AI boom. Microsoft has invested about $13 billion in OpenAI over time -- and through the partnership, it gained access to the AI research lab's models and became its main cloud provider.

On top of this, Microsoft's cloud business is delivering tremendous growth due to its offerings of AI products and services to its customers. In the recent quarter, for example, the AI business' annual revenue run rate topped $37 billion -- that's up 123%. And the entire cloud business delivered quarterly revenue of $54 billion for a 29% increase. Microsoft, as well as other cloud providers and chip companies such as leader Nvidia, have all delivered the same message in recent times: Compute demand for AI workloads continues to soar.

What's weighed on the stock recently

Some investors have shied away from Microsoft in recent months, though, fearing that AI will replace its software in the years to come. This has weighed on the stock, driving it to a 12% decline this year. I don't see AI as a threat since corporate customers have deeply integrated Microsoft's software into their systems -- it's unlikely they would unwind these systems in favor of an AI tool. Instead, the growth in AI may be an opportunity for Microsoft, as the company is integrating AI tools into its software to make this software more and more powerful.

And now that the AI boom is shifting into the era of AI agents, or the software that solves problems and completes tasks, Microsoft could emerge as a big winner. The tech titan is building out cloud infrastructure to support this technology and building agentic systems, too.

Meanwhile, Microsoft stock today trades for 25x forward earnings estimates right now, down from more than 35x about a year ago. This is a fantastic buying opportunity for a company that offers well-established growth drivers as well as leadership in the hot area of AI. And that's why it's the ultimate set-it-and-forget-it AI stock to buy now.