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 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.

Brown Advisory Flexible Equity Adviser (BAFAX Quick QuoteBAFAX - Free Report) : 0.94% expense ratio and 0.43% management fee. BAFAX is classified as an Allocation Balanced fund, which seeks to invest in a balance of asset types, like stocks, bonds, and cash, and including precious metals or commodities is not unusual. BAFAX has achieved five-year annual returns of an astounding 11.83%.

Fidelity Advisor Mega Cap Stock M (FTGRX Quick QuoteFTGRX - Free Report) : 1.16% expense ratio and 0.42% management fee. FTGRX is classified as a Large Cap Blend fund. More often than not, Large Cap Blend mutual funds invest in companies with a market cap of over $10 billion. Buying stakes in bigger companies offer these funds more stability, and are well-suited for investors with a "buy and hold" mindset. With yearly returns of 12.03% over the last five years, FTGRX is an effectively diversified fund with a long reputation of solidly positive performance.

Eaton Vance Atlanta Cap Focus Growth A (EAALX Quick QuoteEAALX - Free Report) is an attractive large-cap allocation. EAALX 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. EAALX has an expense ratio of 1.04%, management fee of 0.65%, and annual returns of 15.17% over the past 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.