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.

AllianzGI Convertible Fund IS (ANNPX Quick QuoteANNPX - Free Report) : 0.71% expense ratio and 0.57% management fee. ANNPX is a Convertible Bonds fund, which are unique investment opportunities because they have both fixed income and equity components, making them hybrid securities. ANNPX has achieved five-year annual returns of an astounding 9.74%.

Congress Large Cap Growth Fund (CAMLX Quick QuoteCAMLX - Free Report) : 0.94% expense ratio and 0.5% management fee. CAMLX 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. CAMLX, with annual returns of 13.74% over the last five years, is a well-diversified fund with a long track record of success.

Columbia Small Cap Value II Class Z (NSVAX Quick QuoteNSVAX - Free Report) . Expense ratio: 1.01%. Management fee: 0.83%. Five year annual return: 8.13%. NSVAX is a Small Cap Value mutual fund option, which typically invest in companies with market caps under $2 billion.

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.