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.

Here are the funds that have achieved the Zacks Mutual Fund Rank #1 (Strong Buy) and have low fees.

Cambiar Opportunity I

(CAMWX Quick QuoteCAMWX - Free Report) : 0.65% expense ratio and 0.6% management fee. CAMWX is a Large Cap Blend fund, targeting companies with market caps of over $10 billion. These funds offer investors a stability, and are perfect for people with a "buy and hold" mindset. CAMWX has achieved five-year annual returns of an astounding 13.32%.

Frost Growth Equity Investor

(FACEX Quick QuoteFACEX - Free Report) : 0.89% expense ratio and 0.5% management fee. FACEX is a Large Cap Growth mutual fund, and these funds invest in many large U.S. firms that are projected to grow at a faster rate than their large-cap peers. With yearly returns of 15.86% over the last five years, FACEX is an effectively diversified fund with a long reputation of solidly positive performance.

Fidelity Equity-Income Fund K

(FEIKX Quick QuoteFEIKX - Free Report) . Expense ratio: 0.48%. Management fee: 0.45%. Five year annual return: 11.8%. FEIKX 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.

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.