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.

If you are looking to diversify your portfolio, consider

Fuller & Thayler Behavioral Small Cap R6

(FTHFX Quick QuoteFTHFX - Free Report) . FTHFX is a Small Cap Blend mutual fund, and usually targets stocks with market caps of less than $2 billion, letting investors diversify their funds among other kinds of small-cap equities. This fund is a winner, boasting an expense ratio of 0.63%, management fee of 0.6%, and a five-year annualized return track record of 16.44%.

Janus Henderson Global Life Science D

(JNGLX Quick QuoteJNGLX - Free Report) : 0.8% expense ratio and 0.64% management fee. JNGLX is a Sector - Health mutual fund, which give investors an opportunity to focus on healthcare, one of the largest sectors of the American economy. With yearly returns of 10.33% over the last five years, JNGLX is an effectively diversified fund with a long reputation of solidly positive performance.

TIAA-CREF Large Cap Value Institutional

(TRLIX Quick QuoteTRLIX - Free Report) . Expense ratio: 0.41%. Management fee: 0.4%. Five year annual return: 12.1%. TRLIX is a Large Cap Value mutual fund, which invests in stocks with a market cap of $10 billion of 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.