Investing in mutual funds for retirement is never too late. And the Zacks Mutual Fund Rank can be an excellent tool for investors looking to invest in the best funds.

The easiest way to judge a mutual fund's quality over time is by analyzing its performance, diversification, and fees. Using the Zacks Mutual Fund 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 break down some of the mutual funds with the top Zacks Mutual Fund Rank and the lowest fees.

RBB Free Market US Equity

(FMUEX Quick QuoteFMUEX - Free Report) : 0.54% expense ratio and 0.49% management fee. FMUEX is an All Cap Growth mutual fund investing in a wide variety of equities, no matter the size of the company and as long as the firm exhibits growth characteristics. With annual returns of 11.9% over the last five years, this fund is a winner.

Oppenheimer Discovery Y

(ODIYX Quick QuoteODIYX - Free Report) is a stand out amongst its peers. ODIYX is a Small Cap Growth mutual fund and tends to feature small companies in up-and-coming industries and markets. With five-year annualized performance of 10.48%, expense ratio of 0.82% and management fee of 0.6%, this diversified fund is an attractive buy with a strong history of performance.

Victory RS Global Growth R

(RGGKX Quick QuoteRGGKX - Free Report) : 1.1% expense ratio and 0.6% management fee. RGGKX is a Global - Equity mutual fund investing in bigger markets like the U.S., Europe, and Japan; these kinds of funds aren't limited by geography. The fund is mainly invested in equities, has a long reputation of salutary performance, and has yearly returns of 13.06% 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.