It's important to stick with what you know when it comes to investing. U.S retirees buying only U.S. stocks makes sense with that in mind. However, a whole world of international stocks awaits investors willing to venture outside the United States. There are risks, of course, but there are also opportunities.

We asked three of our Foolish investors to each put forth an international stock that would be well suited for a retiree's portfolio, safety being the watchword. Here's why retirees should consider Unilever (NYSE:UL), Public Joint-Stock Company Mobile TeleSystems (NYSE:MBT), and Sanofi (NYSE:SNY).

Hands holding flags of different countries.

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A stable of global brands

Tim Green (Unilever): For retirees looking for a relatively safe international stock, Dutch-British consumer-products giant Unilever fits the bill. The company is massive, generating 52 billion euros of revenue last year, and it's wildly profitable, with operating margins consistently in the mid-teens. Unilever owns a massive number of brands, including Dove, Hellmann's, Lipton, Ben & Jerry's, and countless more. According to the company, 2.5 billion people use Unilever products on any given day.

Unilever stock isn't particularly cheap, trading for around 25 times earnings, but paying up for a massive stable of popular and durable brands makes sense. Unilever pays a dividend, with the ADR currently yielding about 2.6%, providing a nice income for retiree shareholders. Currency effects can cause swings in the dividend, but on a constant-currency basis, Unilever's dividend has increased by 7.4% annually between 2010 and 2016.

Unilever's global scale and vast collection of powerful brands give the company important competitive advantages. There's always the risk that some of its brands become stale and susceptible to upstart competitors. But given the breadth of Unilever's business, the company should be able to continue producing exceptional profits for the foreseeable future. Those dividend payments won't stop anytime soon.

This foreign telecom is worth the trip

Rich Smith: (Public Joint-Stock Company Mobile TeleSystems): What should an investor look for in an international stock? At the risk of stating the obvious, I'd say an investor should look for something that he or she cannot find just as easily right here at home.

Think about it. If I tell you that AT&T (NYSE:T) or Verizon (NYSE:VZ) are great stocks for retirees to own, you might respond, "Sure! They both pay good, strong dividends of about 5%.They're not unreasonably expensive at about 12.6 times forward earnings. Those sound like fine stocks for a retiree to own." Or you might say, "No way! T-Mobile is eating their lunch. AT&T and Verizon are doomed!"

Either way, the names are familiar. You know all about the dividends. You know the businesses. You have pretty good insight into whether AT&T and Verizon are good investments. In contrast, with an international stock like Russia's Public Joint-Stock Company Mobile TeleSystems (NYSE:MBT), you probably don't have a lot of firsthand knowledge of the company. To justify investing in an international stock based so far away, you'd want to have a really good incentive for taking on that "unfamiliarity" risk.

So what are your incentives for buying Mobile TeleSystems instead of a domestic telecom? Well, the dividend for one thing. Mobile TeleSystems pays its shareholders a 10% dividend, which is roughly twice the payout at AT&T or Verizon. Growth is another factor in its favor. Analysts expect Mobile TeleSystems to grow its earnings at nearly 10% annually over the next five years -- twice AT&T's expected 5% growth rate, and three times the 3% projected  growth rate at Verizon. Topping it all off, Mobile TeleSystems stock costs only 8.7 times forward earnings -- about 30% cheaper than either AT&T or Verizon.

For a retiree looking to invest in international stocks, I think Mobile TeleSystems is a fine pick.

This French biopharma giant is on the rise

George Budwell (Sanofi): Shares of the French biopharma giant Sanofi have been markedly outperforming most of their large-cap drug-manufacturing peers this year because of the unexpected strength of both Sanofi's vaccine portfolio and an emerging multiple sclerosis franchise. In fact, the drugmaker's shares are currently up close to a healthy 20% so far this year.

A big reason investors have been piling in to this French drugmaker is that the company's newer, long-acting insulin product, Toujeo, has been helping to largely offset the expected decline in the sales of its former flagship diabetes medication, Lantus, that's now under pressure from generic competitors. Previously, industry insiders weren't entirely convinced Toujeo would be up to the task, but the drug's extremely rapid commercial uptake clearly suggests otherwise. 

Apart from Sanofi's proven ability to overcome major new competitive threats to key brands, the company also sports a top-notch dividend yield of 3.4% -- along with a fairly reasonable payout ratio of 79.2%. Many of Sanofi's dividend-paying peers, after all, offer substantially lower yields, but much higher payout ratios to boot. Most importantly, though, Sanofi has raised its payout for 23 consecutive years at this point, showing the company's deep commitment to doling out a top-notch dividend to its shareholders.  

Given Sanofi's strong product portfolio and upper-echelon dividend program, this top international biopharma stock appears to have all the ingredients necessary to be an attractive stock for retired investors on the hunt for relatively safe vehicles to grow their money.  

George Budwell has no position in any of the stocks mentioned. Rich Smith has no position in any of the stocks mentioned. Timothy Green has no position in any of the stocks mentioned. The Motley Fool owns shares of and recommends Verizon Communications. The Motley Fool recommends Unilever. The Motley Fool has a disclosure policy.