The San Francisco Bay area is home to many of the world's great companies. A hotbed of technology and biotech start-ups, the Bay area has no shortage of unprofitable companies burning through cash, but it also has many of the world's most profitable corporations.

Below are the 10 most profitable companies headquartered within the region, ranked by their last reported annual net income.

Company Ticker Net Income (latest annual, in millions USD) Net Profit Margin (latest annual)
Apple (NASDAQ:AAPL) 39,510  21.6%
Wells Fargo (NYSE:WFC) 23,057  27.40%
Google (NASDAQ:GOOG)(NASDAQ:GOOGL) 14,444  21.88%
Gilead Sciences (NASDAQ:GILD) 12,101  48.60%
Oracle (NYSE:ORCL) 10,955  28.62%
Yahoo! (NASDAQ:YHOO) 7,521.7  162.9%
Visa (NYSE:V) 5,438  42.83%
Hewlett-Packard (NYSE:HPQ) 5,013  4.80%
Facebook (NASDAQ:FB) 2,940  23.58%
McKesson (NYSE:MCK) 1,476  0.82%

Source: S&P Capital IQ.

No surprises here
Six of the 10 companies -- Apple, Google, Oracle, Yahoo!, Hewlett-Packard, and Facebook -- are technology companies, which shouldn't be a surprise to anyone familiar with the San Francisco region. 

Apple's fiscal year 2014 was stellar, and fiscal 2015 is shaping up to be even more impressive. It wasn't included in the above figures since the year is not yet complete, but Apple's fiscal year 2015 first quarter was the most profitable in corporate history, and the second quarter was nearly as strong. Demand for the iPhone has fueled Apple's strong profitability and, to some extent, has even benefited several of the other companies on this list. Google, for example, controls the competing Android ecosystem, but it derives about 75% of its mobile search revenue from iPhone users. Facebook generates the bulk -- almost three-quarters -- of its revenue from mobile users, many of them iPhone users.

Percentage wise, all six tech companies on this list have similar net profit margins, with the exception of Yahoo! and Hewlett-Packard. A large percentage of Hewlett-Packard's revenue -- more than half -- comes from its PC and printing businesses, which are mature and notably low margin. Later this year, Hewlett-Packard will split itself in two -- one company (HP) will contain these business segments, the other (HP Enterprise) will focus on enterprise software and services. The latter will have a significantly higher profit margin, but it may not make the list in terms of total net income.

Yahoo!'s shockingly high net profit margin was a byproduct of the sale of its stake in Alibaba. Without that sale, Yahoo!'s net income and profit margin would've been sharply reduced (its 2013 net income, for example, was only $1.366 billion).

Banking and biotech
Of the other four, two are involved in pharmaceuticals (Gilead Sciences and McKesson), and two are financial companies (Visa and Wells Fargo).

Wells Fargo has long been a banking behemoth, and a favorite of billionaire and Berkshire Hathaway (NYSE:BRK-A) (NYSE:BRK-B) CEO Warren Buffett. In fact, Wells Fargo is Berkshire's largest holding. In contrast to other San Francisco companies, which are often on the cutting edge of technology, Wells Fargo operates like a traditional savings and loans company, mostly lending money out to consumers for homes and cars. Buffett also has a stake in Visa, though it's relatively small compared to his Wells Fargo investment.

Gilead Sciences' strong profitability and profit margin come from its deep portfolio of HIV and hepatitis C drugs. McKesson's margins are minuscule, but its business is so enormous (it generated nearly $180 million in revenue in 2015), it still makes this list.

Foolish wrap
One thing from this list is clear: San Francisco is its own epicenter of today's most successful businesses, tech and otherwise.

However, looking at a company's total net income, or even net profit margin, does not tell investors much. Owning shares of an immensely profitable company is ideal, but that profitability may not continue. Rather than stand as a buy or sell recommendation, this list could merely serve as a jumping-off point. Foolish investors know there's more research to be done before making investment decisions.