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.

Harbor Small Cap Growth Investor (HISGX Quick QuoteHISGX - Free Report) : 1.24% expense ratio and 0.75% management fee. HISGX is one of many Small Cap Growth mutual funds; these funds tend to create their portfolios around stocks with market capitalization of less than $2 billion. HISGX has achieved five-year annual returns of an astounding 11.27%.

Principal Large Cap Growth I R4 (PPUSX Quick QuotePPUSX - Free Report) : 0.97% expense ratio and 0.6% management fee. PPUSX is a part of the Large Cap Growth mutual fund category, which invest in many large U.S. companies that are expected to grow much faster compared to other large-cap stocks. With yearly returns of 13.8% over the last five years, PPUSX is an effectively diversified fund with a long reputation of solidly positive performance.

Transamerica Large Cap Value I (TWQIX Quick QuoteTWQIX - Free Report) : 0.64% expense ratio and 0.58% management fee. TWQIX is a Large Cap Value fund. These funds invest in stocks with a market cap of $10 billion of more, but whose share prices do not reflect their intrinsic value. The fund is mainly invested in equities, has a long reputation of salutary performance, and has yearly returns of 8.61% 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.