It is never too late to invest in mutual funds for retirement. As such, if you plan to invest in some of the best funds, the Zacks Mutual Fund Rank can provide you with valuable guidance.

The easiest, most reliable way to judge a mutual fund's quality over time is by analyzing its performance, diversification, and fees. The Zacks Mutual Fund Rank, which covers over 19,000 mutual funds, has helped us identify three outstanding options that are perfect for any long-term investors' portfolios that is retirement-focused.

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

Fidelity OTC Portfolio K (FOCKX Quick QuoteFOCKX - Free Report) : 0.76% expense ratio and 0.68% management fee. FOCKX is a Large Cap Growth option; these mutual funds purchase stakes in numerous large U.S. companies that are expected to develop and grow at a faster rate than other large-cap stocks. FOCKX has achieved five-year annual returns of an astounding 11.67%.

Neuberger Berman Guardian Investor (NGUAX Quick QuoteNGUAX - Free Report) : 0.81% expense ratio and 0.74% management fee. 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. NGUAX, with annual returns of 11.42% over the last five years, is a well-diversified fund with a long track record of success.

Oppenheimer Discovery I (ODIIX Quick QuoteODIIX - Free Report) . Expense ratio: 0.65%. Management fee: 0.59%. Five year annual return: 10.86%. ODIIX is a Small Cap Growth mutual fund and tends to feature small companies in up-and-coming industries and markets.

These examples highlight the fact that there are some astonishingly good mutual funds out there. If your advisor has you in the good ones, bravo! If not, you may need to have a talk.