If you're invested in any of the funds in our "Magnificent Retirement Mutual Funds" list, congratulations on owning some of the best managed and top-performing mutual funds. If you are lucky enough to discover our list of Top-Ranked Funds for the first time, it's never too late to start investing with the best, especially when it comes to your retirement.

The easiest way to judge a mutual fund's quality over time is by analyzing its performance, diversification, and fees. Using our Zacks Rank of over 19,000 mutual funds, we've identified three outstanding mutual funds that are ideally suited to help long-term investors pursue and achieve their retirement investing goals.

Let's learn about some of Zacks' highest ranked mutual funds with low fees you may want to consider.

DFA Enhanced US Large Company I (DFELX Quick QuoteDFELX - Free Report) has a 0.15% expense ratio and 0.12% management fee. DFELX is part of the Large Cap Blend section, and these mutual funds most often invest in firms with a market capitalization of $10 billion or more. By investing in bigger companies, these funds offer more stability, and are often well-suited for investors with a "buy and hold" mindset. With yearly returns of 10.57% over the last five years, this fund clearly wins.

Goldman Sachs Small/Mid-Cap Growth IR (GTMTX Quick QuoteGTMTX - Free Report) : 0.99% expense ratio and 0.85% management fee. GTMTX is a Mid Cap Growth mutual fund. These mutual funds choose companies with a stock market valuation between $2 billion and $10 billion. With yearly returns of 11.19% over the last five years, GTMTX is an effectively diversified fund with a long reputation of solidly positive performance.

Neuberger Berman Guardian Investor (NGUAX Quick QuoteNGUAX - Free Report) . Expense ratio: 0.87%. Management fee: 0.76%. Five year annual return: 12.35%. NGUAX is a part of the Large Cap Value category, and invests in equities with a market capitalization of $10 billion or more, but whose share prices do not reflect their intrinsic value.

So, there you have it - if your advisor has you invested in any of our "Magnificent Retirement Mutual Funds," they are certainly earning their keep. If not, you may want to look elsewhere.

Do You Know the Top 9 Retirement Investing Mistakes?

Investing in underperforming mutual funds is just one of the key errors that can derail your retirement plans.

To learn more, read our just-released report: 9 Retirement Mistakes You Need to Avoid.