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 take a look at some of our top-ranked mutual funds with the lowest fees.

Bridgeway Small Cap Value N (BRSVX Quick QuoteBRSVX - Free Report) has a 0.83% expense ratio and 0.61% management fee. BRSVX is a Small Cap Value mutual fund option, which typically invest in companies with market caps under $2 billion. With yearly returns of 12.96% over the last five years, this fund clearly wins.

Commerce Growth Fund (CFGRX Quick QuoteCFGRX - Free Report) : 0.69% expense ratio and 0.4% management fee. CFGRX 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. CFGRX, with annual returns of 11.77% over the last five years, is a well-diversified fund with a long track record of success.

T. Rowe Price New Horizons (PRNHX Quick QuotePRNHX - Free Report) : 0.8% expense ratio and 0.63% management fee. PRNHX is a Small Cap Growth mutual fund building their portfolio around stocks with market caps under $2 billion and large growth opportunities. The fund is mainly invested in equities, has a long reputation of salutary performance, and has yearly returns of 10.76% over the last five years.

We hope that your investment advisor (if you use one) has you invested in one or all of the top-ranked mutual funds we've reviewed. But if that isn't the case, it might be time to have a conversation or reconsider this vitally important relationship.